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Icaridin, also known as picaridin, is an
insect repellent An insect repellent (also commonly called "bug spray") is a substance applied to skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and cont ...
which can be used directly on skin or clothing. It has broad efficacy against various arthropods such as mosquitos, ticks, gnats, flies and fleas, and is almost colorless and odorless. A study performed in 2010 showed that picaridin spray and cream at the 20% concentration provided 12 hours of protection against ticks. Icaridin does not dissolve plastics, synthetics or sealants. The name ''picaridin'' was proposed as an International Nonproprietary Name (INN) to the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
(WHO), but the official name that has been approved by the
WHO Who or WHO may refer to: * Who (pronoun), an interrogative or relative pronoun * Who?, one of the Five Ws in journalism * World Health Organization Arts and entertainment Fictional characters * Who, a creature in the Dr. Seuss book ''Horton Hear ...
is ''icaridin''. The chemical is part of the
piperidine Piperidine is an organic compound with the molecular formula (CH2)5NH. This heterocyclic amine consists of a six-membered ring containing five methylene bridges (–CH2–) and one amine bridge (–NH–). It is a colorless liquid with an odor des ...
family, along with many pharmaceuticals and
alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar s ...
s such as
piperine Piperine, along with its isomer chavicine, is the alkaloid responsible for the pungency of black pepper and long pepper. It has been used in some forms of traditional medicine. Preparation Due to its poor solubility in water, piperine is typic ...
, which gives
black pepper Black pepper (''Piper nigrum'') is a flowering vine in the family Piperaceae, cultivated for its fruit, known as a peppercorn, which is usually dried and used as a spice and seasoning. The fruit is a drupe (stonefruit) which is about in diame ...
its spicy taste. Trade names include Bayrepel and Saltidin among others. The compound was developed by the German chemical company
Bayer Bayer AG (, commonly pronounced ; ) is a German multinational pharmaceutical and biotechnology company and one of the largest pharmaceutical companies in the world. Headquartered in Leverkusen, Bayer's areas of business include pharmaceutica ...
and was given the name ''Bayrepel''. In 2005,
Lanxess Lanxess AG is a German specialty chemicals company based in Cologne, Germany that was founded in 2004 via the spin-off of the chemicals division and parts of the polymers business from Bayer AG. Shares in Lanxess AG were listed in Germany’s DAX ...
AG and its subsidiary Saltigo GmbH were spun off from Bayer and the product was renamed ''Saltidin'' in 2008. On 23 July 2020, icaridin was approved again by the EU Commission for use in repellent products. The approval entered into force on 1 February 2022 and is valid for ten years.


Effectiveness

Icaridin has been reported to be as effective as
DEET ''N'',''N''-Diethyl-''meta''-toluamide, also called DEET () or diethyltoluamide, is the most common active ingredient in insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection a ...
without the irritation associated with DEET.Journal of Drugs in Dermatology (Jan-Feb 2004) http://jddonline.com/articles/dermatology/S1545961604P0059X/1 According to the WHO, icaridin “demonstrates excellent repellent properties comparable to, and often superior to, those of the standard DEET.” In the United States, the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
recommends using repellents based on icaridin,
DEET ''N'',''N''-Diethyl-''meta''-toluamide, also called DEET () or diethyltoluamide, is the most common active ingredient in insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection a ...
,
ethyl butylacetylaminopropionate Ethyl butylacetylaminopropionate (trade name IR3535) is an insect repellent which is applied topically to prevent bites and stings from mosquitos, ticks, and other insects. It is a colorless and almost odorless oil, has efficacy against a broad ran ...
(IR3535), or oil of
lemon eucalyptus ''Corymbia citriodora'', commonly known as lemon-scented gum and other common names, is a species of tall tree that is endemic to north-eastern Australia. It has smooth white to pink bark, narrow lance-shaped to curved adult leaves, flower buds ...
(containing ''p''-menthane-3,8-diol, PMD) for effective protection against
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 "litt ...
es that carry the
West Nile virus West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family ''Flaviviridae'', from the genus ''Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The virus ...
, eastern equine encephalitis and other illnesses. Icaridin-based products, first used in Europe in 2001, have been evaluated by ''
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization dedicated to independent product testing, investigative journalism, consumer-oriented research, public education, and consumer advocacy. Founde ...
'' in 2016 as among the most effective insect repellents when used at a 20% concentration. Icaridin was earlier reported to be effective by ''
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization dedicated to independent product testing, investigative journalism, consumer-oriented research, public education, and consumer advocacy. Founde ...
'' (7% solution) and the Australian Army (20% solution). ''Consumer Reports'' retests in 2006 gave as result that a 7% solution of icaridin offered little or no protection against ''
Aedes ''Aedes'' is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except perhaps Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', a particularly invasive spe ...
'' mosquitoes (vector of
dengue fever Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic ...
) and a protection time of about 2.5 hours against ''
Culex ''Culex'' is a genus of mosquitoes, several species of which serve as vectors of one or more important diseases of birds, humans, and other animals. The diseases they vector include arbovirus infections such as West Nile virus, Japanese ence ...
'' (vector of West Nile virus), while a 15% solution was good for about one hour against ''Aedes'' and 4.8 hours against ''Culex''.


Larval salamander toxicity

A 2018 study found that a commercial repellent product containing 20% icaridin, in what the authors described as "conservative exposure doses", is highly toxic to
salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All te ...
larvae. Since only the icaridin content of the tested repellent product is known, the observed effects cannot be readily attributed to icaridin. Furthermore, the effects of the repellent product showed no dose-response relationship, i.e., there was neither an increase of the magnitude or severity of the observed effects (mortality, tail deformation), nor did the effects occur at earlier time points. The study has been regarded as invalid by the Danish Environmental Protection Agency, which has evaluated icaridin prior to its approval under the EU Biocidal Product Regulation. The reasons for rejection were the testing of a mixture of undisclosed composition, the use of a non-standard test organism, the lack of analytical verification of actual test concentrations, and the fact that the test solution was never renewed with the 25 days of study duration. The study observed high larval salamander mortality occurring delayed after the four days of exposure. Because the widely used LC50 test for assessing a chemical's environmental toxicity is based on mortality within four days, the authors suggested that icaridin would be incorrectly deemed as "safe" under the test protocol. However, icaridin was also non-toxic in a 21-day reproduction test on the water flea ''Daphnia magna'' and a 32-day early life-stage test in zebrafish.


Chemistry

Icaridin contains two
stereocenter In stereochemistry, a stereocenter of a molecule is an atom (center), axis or plane that is the focus of stereoisomerism; that is, when having at least three different groups bound to the stereocenter, interchanging any two different groups c ...
s: one where the hydroxyethyl chain attaches to the ring, and one where the ''sec''-butyl attaches to the oxygen of the
carbamate In organic chemistry, a carbamate is a category of organic compounds with the general formula and structure , which are formally derived from carbamic acid (). The term includes organic compounds (e.g., the ester ethyl carbamate), formally ob ...
. The commercial material contains a mixture of all four stereoisomers.


Commercial products

Commercial products containing icaridin include Cutter Advanced, Muskol, Skin So Soft Bug Guard Plus, Off! FamilyCare, Autan, Smidge, PiActive and MOK.O.


Mechanism

A potential odorant receptor for icaridin (and DEET), the CquiOR136•CquiOrco, has been suggested recently for ''Culex quinquefasciatus'' mosquito. Recent crystal and solution studies showed that icaridin binds to ''Anopheles gambiae'' odorant binding protein 1 (AgamOBP1). The crystal structure of AgamOBP1•icaridin complex (PDB
5EL2
revealed that icaridin binds to the DEET-binding site in two distinct orientations and also to a second binding site (sIC-binding site) located at the C-terminal region of the AgamOBP1. Recent evidence with ''
Anopheles gambiae The ''Anopheles gambiae'' complex consists of at least seven morphologically indistinguishable species of mosquitoes in the genus ''Anopheles''. The complex was recognised in the 1960s and includes the most important vectors of malaria in sub- ...
'' mosquitoes suggests icaridin does not strongly activate olfactory receptors neurons, but instead functions to reduce the volatility of the odorants to which it is mixed.{{Cite journal, last1=Afify, first1=Ali, last2=Betz, first2=Joshua F., last3=Riabinina, first3=Olena, last4=Lahondère, first4=Chloé, last5=Potter, first5=Christopher J., date=2019, title=Commonly Used Insect Repellents Hide Human Odors from Anopheles Mosquitoes, journal=Current Biology, language=en, volume=29, issue=21, pages=3669–3680.e5, doi=10.1016/j.cub.2019.09.007, pmid=31630950, pmc=6832857 By reducing odor volatility, icaridin functions to "mask" the ability of volatile odorants on the skin to activate olfactory neurons and attract mosquitoes.


See also

*
SS220 SS220 is an insect repellent with a broad range of efficacy. It was developed in 2002 at the ''Chemicals Affecting Insect Behavior Laboratory'' of the United States Department of Agriculture and has been found to "exert repellent and deterrent ef ...
, another substituted-piperidine insect repellent


References


External links


Picaridin General Fact Sheet - National Pesticide Information Center


* ttps://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-070705_01-May-05.pdf EPA fact sheet Household chemicals Insect repellents Carbamates Piperidines Primary alcohols