An allergen is a type of
antigen
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
that produces an abnormally vigorous
immune response
An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...
in which the
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called
allergies
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...
.
In technical terms, an allergen is an antigen that is capable of stimulating a
type-I hypersensitivity
Type I hypersensitivity (or immediate hypersensitivity), in the Gell and Coombs classification of allergic reactions, is an allergic reaction provoked by re-exposure to a specific type of antigen referred to as an allergen. Type I is distinct fro ...
reaction in
atopic
Atopy is the tendency to produce an exaggerated immunoglobulin E (IgE) immune response to otherwise harmless substances in the environment. Allergic diseases are clinical manifestations of such inappropriate, atopic responses.
Atopy may have a ...
individuals through
immunoglobulin E
Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) " isotype") that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the ε c ...
(IgE) responses. Most humans mount significant Immunoglobulin E responses only as a defense against
parasitic infection
A parasitic disease, also known as parasitosis, is an infectious disease caused by parasites. Parasites are organisms which derive sustenance from its host while causing it harm. The study of parasites and parasitic diseases is known as parasitolo ...
s. However, some individuals may respond to many common environmental antigens. This hereditary predisposition is called
atopy
Atopy is the tendency to produce an exaggerated immunoglobulin E (IgE) immune response to otherwise harmless substances in the environment. Allergic diseases are clinical manifestations of such inappropriate, atopic responses.
Atopy may have a ...
. In atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity.
Sensitivities vary widely from one person (or from one animal) to another. A very broad range of substances can be allergens to sensitive individuals.
Types of allergens
Allergens can be found in a variety of sources, such as
dust mite
House dust mites (HDM, or simply dust mites) are various species of acariform mites belonging to the family Pyroglyphidae that are found in association with dust in dwellings. They are known for causing allergies.
Biology
Species
The curren ...
excretion,
pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
, pet
dander
Dander is material shed from the body of humans and other animals that have fur, hair, or feathers. The term is similar to dandruff, when an excess of flakes becomes visible. Skin flakes that come off the main body of an animal are dander, while th ...
, or even
royal jelly
Royal jelly is a honey bee secretion that is used in the nutrition of larvae and adult queens. It is secreted from the glands in the hypopharynx of nurse bees, and fed to all larvae in the colony, regardless of sex or caste.Graham, J. (ed.) (19 ...
. Food allergies are not as common as
food sensitivity
Food intolerance is a detrimental reaction, often delayed, to a food, beverage, food additive, or compound found in foods that produces symptoms in one or more body organs and systems, but generally refers to reactions other than food allergy. Fo ...
, but some foods such as
peanut
The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible Seed, seeds. It is widely grown in the tropics and subtropics, important to both small ...
s (a
legume
A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...
),
nut
Nut often refers to:
* Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds
* Nut (hardware), fastener used with a bolt
Nut or Nuts may also refer to:
Arts, entertainment, and media Co ...
s,
seafood
Seafood is any form of sea life regarded as food by humans, prominently including fish and shellfish. Shellfish include various species of molluscs (e.g. bivalve molluscs such as clams, oysters and mussels, and cephalopods such as octopus an ...
and
shellfish
Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater envir ...
are the cause of serious allergies in many people.
Officially, the United States
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
does recognize eight foods as being common for allergic reactions in a large segment of the sensitive population. These include peanuts, tree nuts, eggs, milk, shellfish, fish, wheat and their derivatives, and soy and their derivatives, as well as sulfites (chemical-based, often found in flavors and colors in foods) at 10ppm and over. See the FDA website for complete details. In other countries, due to differences in the genetic profiles of their citizens and different levels of exposure to specific foods resultant from different dietary habits, the "official" allergen lists will vary. Canada recognizes all eight of the allergens recognized by the US as well as sesame seeds and mustard. The
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
additionally recognizes other
gluten-containing cereals as well as celery and
lupin
''Lupinus'', commonly known as lupin, lupine, or regionally bluebonnet etc., is a genus of plants in the legume family Fabaceae. The genus includes over 199 species, with centers of diversity in North and South America. Smaller centers occur ...
.
Another allergen is
urushiol
Urushiol is an oily mixture of organic compounds with allergenic properties found in plants of the family Anacardiaceae, especially '' Toxicodendron'' ''spp.'' (e.g., poison oak, Chinese lacquer tree, poison ivy, poison sumac), ''Comoclad ...
, a resin produced by
poison ivy and
poison oak Poison oak refers to two plant species in the genus ''Toxicodendron,'' both of which can cause skin irritation:
*''Toxicodendron diversilobum'' or Western poison oak, found in western North America
*''Toxicodendron pubescens
''Toxicodendron pub ...
, which causes the skin rash condition known as
urushiol-induced contact dermatitis
Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis or Rhus dermatitis) is a type of allergic contact dermatitis caused by the oil urushiol found in various plants, most notably species of the genus '' Toxicodendron'': pois ...
by changing a skin cell's configuration so that it is no longer recognized by the immune system as part of the body. Various trees and wood products such as paper, cardboard, MDF etc. can also cause mild to severe allergy symptoms through touch or inhalation of sawdust such as asthma and skin rash.
An allergic reaction can be caused by any form of direct contact with the allergen—consuming food or drink one is sensitive to (ingestion), breathing in pollen, perfume or pet dander (inhalation), or brushing a body part against an allergy-causing plant (direct contact). Other common causes of serious allergy are
wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...
,
fire ant
Fire ants are several species of ants in the genus ''Solenopsis'', which includes over 200 species. ''Solenopsis'' are stinging ants, and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many of the nam ...
and
bee stings,
penicillin
Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
, and
latex
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
. An extremely serious form of an allergic reaction is called
anaphylaxis
Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follow ...
. One form of treatment is the administration of sterile
epinephrine
Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...
to the person experiencing anaphylaxis, which suppresses the body's overreaction to the allergen, and allows for the patient to be transported to a medical facility.
Common allergens
![Peanuts, Egg, and Milk (33000737773)](https://upload.wikimedia.org/wikipedia/commons/3/30/Peanuts%2C_Egg%2C_and_Milk_%2833000737773%29.jpg)
In addition to foreign proteins found in foreign serum (from
blood transfusion
Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...
s) and
vaccine
A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...
s, common allergens include:
* Animal products
**
Fel d 1
Fel d 1 is a secretoglobin protein complex that, in cats, is encoded by the ''CH1'' (chain 1/Fel d 1-A) and ''CH2'' (chain 2/Fel d 1-B) genes.
Among cats, Fel d 1 is produced largely in their saliva and by the sebaceous glands located in the ...
(
Allergy to cats
Allergies to cats are one of the most common allergies among human individuals. Among the eight known cat allergens, the most prominent allergen is secretoglobin Fel d 1, which is produced in the anal glands, salivary glands, and, mainly, in sebace ...
)
**
fur
Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...
and
dander
Dander is material shed from the body of humans and other animals that have fur, hair, or feathers. The term is similar to dandruff, when an excess of flakes becomes visible. Skin flakes that come off the main body of an animal are dander, while th ...
**
cockroach
Cockroaches (or roaches) are a paraphyletic group of insects belonging to Blattodea, containing all members of the group except termites. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known as ...
calyx
**
wool
Wool is the textile fibre obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have properties similar to animal wool.
As ...
**
dust mite
House dust mites (HDM, or simply dust mites) are various species of acariform mites belonging to the family Pyroglyphidae that are found in association with dust in dwellings. They are known for causing allergies.
Biology
Species
The curren ...
excretion
*
Drug
A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffla ...
s
**
penicillin
Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
**
sulfonamides
In organic chemistry, the sulfonamide functional group (also spelled sulphonamide) is an organosulfur group with the structure . It consists of a sulfonyl group () connected to an amine group (). Relatively speaking this group is unreactive. ...
**
salicylate
Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substance ...
s (also found naturally in numerous
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
s)
*
Food
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...
s
**
celery
Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, lea ...
and
celeriac
Celeriac (''Apium graveolens'' var. ''rapaceum''), also called celery root, knob celery, and turnip-rooted celery (although it is not a close relative of the turnip), is a variety of celery cultivated for its edible stem or hypocotyl, and shoo ...
**
corn
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maÃz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
or
maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maÃz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
**
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s (typically
albumen
Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms arou ...
, the white)
**
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
***
pumpkin
A pumpkin is a vernacular term for mature winter squash of species and varieties in the genus ''Cucurbita'' that has culinary and cultural significance but no agreed upon botanical or scientific meaning. The term ''pumpkin'' is sometimes use ...
, egg-plant
**
legume
A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...
s
***
bean
A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...
s
***
pea
The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...
s
***
peanut
The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible Seed, seeds. It is widely grown in the tropics and subtropics, important to both small ...
s
***
soybean
The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses.
Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...
s
**
milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digestion, digest solid food. Immune factors and immune ...
**
seafood
Seafood is any form of sea life regarded as food by humans, prominently including fish and shellfish. Shellfish include various species of molluscs (e.g. bivalve molluscs such as clams, oysters and mussels, and cephalopods such as octopus an ...
**
sesame
Sesame ( or ; ''Sesamum indicum'') is a flowering plant in the genus ''Sesamum'', also called benne. Numerous wild relatives occur in Africa and a smaller number in India. It is widely naturalized in tropical regions around the world and is cu ...
**
soy
The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses.
Traditional unfermented food uses of soybeans include soy milk, from which tofu and ...
**
tree nut
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are u ...
s
***
pecan
The pecan (''Carya illinoinensis'') is a species of hickory native to the southern United States and northern Mexico in the region of the Mississippi River. The tree is cultivated for its seed in the southern United States, primarily in Georgia, ...
s
***
almond
The almond (''Prunus amygdalus'', syn. ''Prunus dulcis'') is a species of tree native to Iran and surrounding countries, including the Levant. The almond is also the name of the edible and widely cultivated seed of this tree. Within the genus ...
s
**
wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
*
Insect stings
**
bee sting
venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
**
wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...
sting venom
**
mosquito
Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
bites
* Mold
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
s
* Top 5 allergens discovered in
patch tests in 2005–06:
**
nickel sulfate
Nickel(II) sulfate, or just nickel sulfate, usually refers to the inorganic compound with the formula NiSO4(H2O)6. This highly soluble blue green coloured salt is a common source of the Ni2+ ion for electroplating.
Approximately 40,000 tonnes ...
(19.0%)
**
Balsam of Peru
Balsam of Peru or Peru balsam, also known and marketed by many other names, is a balsam derived from a tree known as ''Myroxylon balsamum'' var. ''pereirae''; it is found in El Salvador, where it is an endemic species.
Balsam of Peru is used i ...
(11.9%)
**
fragrance
An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently vol ...
mix I (11.5%)
**
quaternium-15
Quaternium-15 (systematic name: hexamethylenetetramine chloroallyl chloride) is a quaternary ammonium salt that has been used as a surfactant and preservative. It acts as an antimicrobial agent because it slowly releases formaldehyde, which is a ...
(10.3%), and
**
neomycin
Neomycin is an aminoglycoside antibiotic that displays bactericidal activity against gram-negative aerobic bacilli and some anaerobic bacilli where resistance has not yet arisen. It is generally not effective against gram-positive bacilli and ...
(10.0%).
[Zug KA, Warshaw EM, Fowler JF Jr, Maibach HI, Belsito DL, Pratt MD, Sasseville D, Storrs FJ, Taylor JS, Mathias CG, Deleo VA, Rietschel RL, Marks J. Patch-test results of the North American Contact Dermatitis Group 2005–2006. Dermatitis. 2009 May–Jun;20(3):149-60.]
* Metals
**
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
**
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
* Other
**
latex
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
**
wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
* Plant
pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
s (
hay fever
Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, i ...
)
**
grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...
—
ryegrass
''Lolium'' is a genus of tufted grasses in the bluegrass subfamily (Pooideae). It is often called ryegrass, but this term is sometimes used to refer to grasses in other genera.
They are characterized by bunch-like growth habits. ''Lolium'' is ...
,
timothy-grass
Timothy (''Phleum pratense'') is an abundant perennial grass native to most of Europe except for the Mediterranean region. It is also known as timothy-grass, meadow cat's-tail or common cat's tail. It is a member of the genus ''Phleum'', consi ...
**
weed
A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...
s —
ragweed
Ragweeds are flowering plants in the genus ''Ambrosia'' in the aster family, Asteraceae. They are distributed in the tropical and subtropical regions of the Americas, especially North America,[plantago
''Plantago'' is a genus of about 200 species of flowering plants in the family Plantaginaceae, commonly called plantains or fleaworts. The common name plantain is shared with the unrelated cooking plantain. Most are herbaceous plants, though ...]
,
nettle
{{redirect, Nettle
Nettle refers to plants with stinging hairs, particularly those of the genus '' Urtica''. It can also refer to plants which resemble ''Urtica'' species in appearance but do not have stinging hairs. Plants called "nettle" includ ...
, ''
Artemisia vulgaris'', ''
Chenopodium album
''Chenopodium album'' is a fast-growing weedy annual plant in the genus ''Chenopodium''. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb's quarters, melde, goosefoot, wild spinach and fat-h ...
'',
sorrel
Sorrel (''Rumex acetosa''), also called common sorrel or garden sorrel, is a perennial herbaceous plant in the family Polygonaceae. Other names for sorrel include spinach dock and narrow-leaved dock ('dock' being a common name for the genus '' ...
**
tree
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
s —
birch
A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...
,
alder
Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...
,
hazel
The hazel (''Corylus'') is a genus of deciduous trees and large shrubs native to the temperate Northern Hemisphere. The genus is usually placed in the birch family Betulaceae,Germplasmgobills Information Network''Corylus''Rushforth, K. (1999). ...
,
hornbeam
Hornbeams are hardwood trees in the flowering plant genus ''Carpinus'' in the birch family Betulaceae. The 30–40 species occur across much of the temperate regions of the Northern Hemisphere.
Origin of names
The common English name ''hornbeam' ...
, ''
Aesculus
The genus ''Aesculus'' ( or ), with species called buckeye and horse chestnut, comprises 13–19 species of flowering plants in the family Sapindaceae. They are trees and shrubs native plant, native to the temperateness, temperate Northern H ...
'',
willow
Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist s ...
,
poplar, ''
Platanus
''Platanus'' is a genus consisting of a small number of tree species native to the Northern Hemisphere. They are the sole living members of the family Platanaceae.
All mature members of ''Platanus'' are tall, reaching in height. All except f ...
'', ''
Tilia
''Tilia'' is a genus of about 30 species of trees or bushes, native throughout most of the temperateness, temperate Northern Hemisphere. The tree is known as linden for the European species, and basswood for North American species. In Britain a ...
'', ''
Olea
''Olea'' ( ) is a genus of about 40 species in the family Oleaceae, native to warm temperate and tropical regions of the Middle East, southern Europe, Africa, southern Asia, and Australasia. They are evergreen trees and shrubs, with small ...
'',
Ashe juniper
''Juniperus ashei'' (Ashe juniper, mountain cedar, blueberry juniper, post cedar, or just cedar) is a drought-tolerant evergreen tree, native from northeastern Mexico and the south-central United States to southern Missouri. The largest areas are ...
, ''Alstonia scholaris''
Seasonal allergy
Seasonal allergy symptoms are commonly experienced during specific parts of the year, usually during spring, summer or fall when certain trees or grasses pollinate. This depends on the kind of tree or grass. For instance, some trees such as
oak
An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
,
elm
Elms are deciduous and semi-deciduous trees comprising the flowering plant genus ''Ulmus'' in the plant family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical-montane regions of North ...
, and
maple
''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since http ...
pollinate in the spring, while grasses such as
Bermuda
)
, anthem = "God Save the King"
, song_type = National song
, song = " Hail to Bermuda"
, image_map =
, map_caption =
, image_map2 =
, mapsize2 =
, map_caption2 =
, subdivision_type = Sovereign state
, subdivision_name =
, e ...
, timothy and orchard pollinate in the summer.
Grass allergy is generally linked to hay fever because their symptoms and causes are somehow similar to each other. Symptoms include
rhinitis
Rhinitis, also known as coryza, is irritation and inflammation of the mucous membrane inside the nose. Common symptoms are a stuffy nose, runny nose, sneezing, and post-nasal drip.
The inflammation is caused by viruses, bacteria, irritants o ...
, which causes
sneezing
A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth and ...
and a
runny nose
Rhinorrhea, rhinorrhoea, or informally runny nose is the free discharge of a thin mucus fluid from the nose; it is a common condition. It is a common symptom of allergies ( hay fever) or certain viral infections, such as the common cold or COVI ...
, as well as
allergic conjunctivitis
Allergic conjunctivitis (AC) is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist of redness (mainly due ...
, which includes watering and itchy eyes.
Also an initial tickle on the roof of the mouth or in the back of the throat may be experienced.
Also, depending on the season, the symptoms may be more severe and people may experience
coughing,
wheezing
A wheeze is a continuous, coarse, whistling sound produced in the respiratory airways during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed or obstructed (for example narrowing of the lower respiratory tract ...
, and irritability. A few people even become depressed, lose their
appetite
Appetite is the desire to eat food items, usually due to hunger. Appealing foods can stimulate appetite even when hunger is absent, although appetite can be greatly reduced by satiety. Appetite exists in all higher life-forms, and serves to regu ...
, or have problems sleeping. Moreover, since the
sinuses
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoid ...
may also become congested, some people experience
headaches
Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches.
Headaches can occur as a result of m ...
.
If both parents have had allergies in the past, there is a 66% chance for the individual to experience seasonal allergies, and the risk lowers to 60% if just one parent has had allergies. The immune system also has strong influence on seasonal allergies, because it reacts differently to diverse allergens like pollen. When an allergen enters the body of an individual that is predisposed to allergies, it triggers an immune reaction and the production of antibodies. These allergen antibodies migrate to mast cells lining the nose, eyes, and lungs. When an allergen drifts into the nose more than once, mast cells release a slew of chemicals or histamines that irritate and inflame the moist membranes lining the nose and produce the symptoms of an allergic reaction: scratchy throat, itching, sneezing and watery eyes. Some symptoms that differentiate allergies from a cold include:
* No fever.
* Mucous secretions are runny and clear.
* Sneezes occurring in rapid and several sequences.
* Itchy throat, ears and nose.
* These symptoms usually last longer than 7–10 days.
Among seasonal allergies, there are some allergens that fuse together and produce a new type of allergy. For instance, grass pollen allergens cross-react with food allergy proteins in vegetables such as onion, lettuce, carrots, celery, and corn. Besides, the cousins of birch pollen allergens, like apples, grapes, peaches, celery, and apricots, produce severe itching in the ears and throat. The cypress pollen allergy brings a cross reactivity between diverse species like olive, privet, ash and Russian olive tree pollen allergens. In some rural areas, there is another form of seasonal grass allergy, combining airborne particles of pollen mixed with mold.
Recent research has suggested that humans might develop allergies as a defense to fight off parasites. According to Yale University Immunologist Dr
Ruslan Medzhitov
Ruslan Maksutovich Medzhitov (born March 12, 1966) is a professor of immunobiology at Yale School of Medicine, a member of Yale Cancer Center, and a Howard Hughes Medical Institute investigator. His research focuses on the analysis of the innate i ...
, protease allergens cleave the same sensor proteins that evolved to detect proteases produced by the parasitic worms. Additionally, a new report on seasonal allergies called "Extreme allergies and Global Warming", have found that many allergy triggers are worsening due to climate change. 16 states in the United States were named as "Allergen Hotspots" for large increases in allergenic tree pollen if global warming pollution keeps increasing. Therefore, researchers on this report claimed that global warming is bad news for millions of asthmatics in the United States whose asthma attacks are triggered by seasonal allergies. Indeed, seasonal allergies are one of the main triggers for asthma, along with colds or flu, cigarette smoke and exercise. In Canada, for example, up to 75% of asthmatics also have seasonal allergies.
Seasonal allergy diagnosis
Based on the symptoms seen on the patient, the answers given in terms of symptom evaluation and a physical exam, doctors can make a diagnosis to identify if the patient has a seasonal allergy. After performing the diagnosis, the doctor is able to tell the main cause of the allergic reaction and recommend the treatment to follow. 2 tests have to be done in order to determine the cause: a blood test and a skin test. Allergists do skin tests in one of two ways: either dropping some purified liquid of the allergen onto the skin and pricking the area with a small needle; or injecting a small amount of allergen under the skin.
Alternative tools are available to identify seasonal allergies, such as laboratory tests, imaging tests, and nasal endoscopy. In the laboratory tests, the doctor will take a nasal smear and it will be examined microscopically for factors that may indicate a cause: increased numbers of eosinophils (white blood cells), which indicates an allergic condition. If there is a high count of eosinophils, an allergic condition might be present.
Another laboratory test is the blood test for IgE (immunoglobulin production), such as the
radioallergosorbent test
A radioallergosorbent test (RAST) is a blood test using radioimmunoassay test to detect specific IgE antibodies in order to determine the substances a subject is allergic to. This is different from a skin allergy test, which determines allergy by ...
(RAST) or the more recent enzyme allergosorbent tests (EAST), implemented to detect high levels of allergen-specific IgE in response to particular allergens. Although blood tests are less accurate than the skin tests, they can be performed on patients unable to undergo skin testing. Imaging tests can be useful to detect sinusitis in people who have chronic rhinitis, and they can work when other test results are ambiguous. There is also nasal endoscopy, wherein a tube is inserted through the nose with a small camera to view the passageways and examine any irregularities in the nose structure. Endoscopy can be used for some cases of chronic or unresponsive seasonal rhinitis.
Fungal allergens
In 1952
basidiospores were described as being possible airborne allergens and were linked to asthma in 1969. Basidiospores are the dominant airborne fungal allergens. Fungal allergies are associated with seasonal asthma. They are considered to be a major source of airborne allergens.
The basidospore family include mushrooms, rusts, smuts, brackets, and
puffballs
Puffballs are a type of fungus featuring a ball-shaped fruit body that bursts on impact, releasing a cloud of dust-like spores when mature. Puffballs belong to the division Basidiomycota and encompass several genera, including ''Calvatia'', ''Ca ...
. The airborne spores from mushrooms reach levels comparable to those of mold and pollens. The levels of mushroom respiratory allergy are as high as 30 percent of those with allergic disorder, but it is believed to be less than 1 percent of food allergies. Heavy rainfall (which increases fungal spore release) is associated with increased hospital admissions of children with asthma. A study in New Zealand found that 22 percent of patients with respiratory allergic disorders tested positive for basidiospores allergies.
Mushroom spore allergies can cause either immediate allergic symptomatology or delayed allergic reactions. Those with asthma are more likely to have immediate allergic reactions and those with allergic rhinitis are more likely to have delayed allergic responses. A study found that 27 percent of patients were allergic to basidiomycete mycelia extracts and 32 percent were allergic to basidiospore extracts, thus demonstrating the high incidence of fungal sensitisation in individuals with suspected allergies. It has been found that of basidiomycete cap, mycelia, and spore extracts that spore extracts are the most reliable extract for diagnosing basidiomycete allergy.
In Canada, 8% of children attending allergy clinics were found to be allergic to
Ganoderma
''Ganoderma'' is a genus of polypore fungi in the family Ganodermataceae that includes about 80 species, many from tropical regions. They have a high genetic diversity and are used in traditional Asian medicines. ''Ganoderma'' can be differenti ...
, a basidiospore.
Pleurotus ostreatus
''Pleurotus ostreatus'', the oyster mushroom, oyster fungus, or hiratake, is a common edible mushroom. It was first cultivated in Germany as a subsistence measure during World War I and is now grown commercially around the world for food. It is ...
,
cladosporium
''Cladosporium'' is a genus of fungi including some of the most common indoor and outdoor molds. Species produce olive-green to brown or black colonies, and have dark-pigmented conidia that are formed in simple or branching chains. Many species ...
, and ''
Calvatia cyathiformis
''Calvatia cyathiformis'', or purple-spored puffball, is a large edible saprobic species of ''Calvatia''. This terrestrial puffball has purplish or purple-brown spores, which distinguish it from other large Agaricales. It is found mostly in prairi ...
'' are significant airborne spores.
Other significant fungal allergens include
aspergillus
' () is a genus consisting of several hundred mold species found in various climates worldwide.
''Aspergillus'' was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Miche ...
and
alternaria
''Alternaria'' is a genus of Deuteromycetes fungi. All species are known as major plant pathogens. They are also common allergens in humans, growing indoors and causing hay fever or hypersensitivity reactions that sometimes lead to asthma. They ...
-
penicillin
Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
families. In India ''
Fomes pectinatus'' is a predominant air-borne allergen affecting up to 22 percent of patients with respiratory allergies. Some fungal air-borne allergens such as ''
Coprinus comatus'' are associated with worsening of
eczema
Dermatitis is inflammation of the Human skin, skin, typically characterized by itchiness, erythema, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become lichenification, thick ...
tous skin lesions.
Children who are born during autumn months (during fungal spore season) are more likely to develop asthmatic symptoms later in life.
Treatment
Treatment includes
over-the-counter medication
Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid prescr ...
s,
antihistamines
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides re ...
,
nasal decongestants Topical decongestants are decongestants applied directly to the nasal cavity. Their effectiveness by themselves in the common cold appears to have a small benefit in adults.
Topical decongestants should only be used by patients for a maximum of 5†...
,
allergy shots, and
alternative medicine
Alternative medicine is any practice that aims to achieve the healing effects of medicine despite lacking biological plausibility, testability, repeatability, or evidence from clinical trials. Complementary medicine (CM), complementary and alt ...
. In the case of nasal symptoms, antihistamines are normally the first option. They may be taken together with
pseudoephedrine
Pseudoephedrine (PSE) is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It may be used as a nasal/sinus decongestant, as a stimulant, or as a wakefulness-promoting agent in higher doses.
It was first characteri ...
to help relieve a stuffy nose and they can stop the itching and sneezing. Some over-the-counter options are
Benadryl
Benadryl is a brand of various antihistamine medications used to stop allergies, whose content varies in different countries, but which includes some combination of diphenhydramine, acrivastine, and/or cetirizine.
It is sold by Johnson & Johnso ...
and
Tavist
Clemastine, also known as meclastin, is a first-generation H1 histamine antagonist (antihistamine) with anticholinergic properties (drying) and sedative side effects. Like all first-generation antihistamines, it is sedating.
Patented in 1960 ...
. However, these antihistamines may cause extreme drowsiness, therefore, people are advised to not operate heavy machinery or drive while taking this kind of medication. Other side effects include dry
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
, blurred vision,
constipation
Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement ...
, difficulty with
urination
Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...
, confusion, and light-headedness.
There is also a newer second generation of antihistamines that are generally classified as the "
non-sedating antihistamines
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides ...
" or anti-drowsy, which include
cetirizine
Cetirizine, sold under the brand name Zyrtec among others, is a second-generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria (hives). It is taken by mouth. Effects generally begin within thirty minutes a ...
,
loratadine
Loratadine, sold under the brand name Claritin among others, is a medication used to treat allergies. This includes allergic rhinitis (hay fever) and hives. It is also available in combination with pseudoephedrine, a decongestant, known as lora ...
, and
fexofenadine
Fexofenadine, sold under the brand name Allegra among others, is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.
Therapeutically, fexofenadine is a selective peripheral H1 block ...
.
An example of nasal decongestants is pseudoephedrine and its side-effects include
insomnia
Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...
,
restlessness, and difficulty urinating. Some other
nasal spray
Nasal sprays are used to deliver medications locally in the nasal cavities or systemically. They are used locally for conditions such as nasal congestion and allergic rhinitis. In some situations, the nasal delivery route is preferred for syste ...
s are available by prescription, including
Azelastine and
Ipratropium
Ipratropium bromide, sold under the trade name Atrovent among others, is a type of anticholinergic (SAMA: short acting muscarinic antagonist) medication which opens up the medium and large airways in the lungs. It is used to treat the symptoms ...
. Some of their side-effects include drowsiness. For eye symptoms, it is important to first bath the eyes with plain eyewashes to reduce the irritation. People should not wear
contact lenses
Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic ...
during episodes of conjunctivitis.
Allergen immunotherapy
Allergen immunotherapy, also known as desensitization or hypo-sensitization, is a medical treatment for environmental allergies, such as insect bites, and asthma. Immunotherapy involves exposing people to larger and larger amounts of allergen in ...
treatment involves administering doses of allergens to accustom the body to induce specific long-term tolerance.
[Van Overtvelt L. et al. Immune mechanisms of allergen-specific sublingual immunotherapy. Revue française d'allergologie et d'immunologie clinique. 2006; 46: 713–720.] Allergy immunotherapy can be administered orally (as sublingual tablets or sublingual drops), or by injections under the skin (subcutaneous). Immunotherapy contains a small amount of the substance that triggers the allergic reactions.
See also
*
Asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
*
Bioaerosol Bioaerosols (short for biological aerosols) are a subcategory of particles released from terrestrial and marine ecosystems into the atmosphere. They consist of both living and non-living components, such as fungi, pollen, bacteria and viruses. Comm ...
*
Eczema
Dermatitis is inflammation of the Human skin, skin, typically characterized by itchiness, erythema, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become lichenification, thick ...
*
Eggshell skull
The eggshell rule (also thin skull rule, papier-mâché-plaintiff rule, or talem qualem rule) is a well-established legal doctrine in common law, used in some tort law systems, with a similar doctrine applicable to criminal law. The rule stat ...
*
Hypoallergenic
Hypoallergenic, meaning "below average" or "slightly" allergenic, is a term meaning that something (usually cosmetics, pets, textiles, food, etc.) causes fewer allergic reactions. The term was first used in 1953 in an advertising campaign for cosm ...
*
Immunodiagnostics
*
List of allergies
This is a list of allergies, which includes the allergen, potential reactions, and a brief description of the cause where applicable.
Allergens
Food
Medical
Environmental
Contact
Many substances can cause an allergic reaction when in c ...
*
Nose filter
A nose filter or nasal filter is an air filter designed to fit inside the human nostrils to prevent the nasal inhalation of allergen
An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune sy ...
*
Oral allergy syndrome
Oral allergy syndrome (OAS) or pollen-food allergy is a type of food allergy classified by a cluster of allergic reactions in the mouth and throat in response to eating certain (usually fresh) fruits, nuts, and vegetables that typically develops ...
*
Toxin
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...
References
External links
General information on allergy and allergensAllermatch — Sequence comparison to allergenic proteinsSDAP — Structural database of allergenic proteinsAllergome DatabaseAllergen Nomenclature
{{Authority control
Immune system
Immunology
Allergology