Light therapy, also called phototherapy or bright light therapy is intentional daily exposure to direct sunlight or similar-intensity artificial light in order to treat medical disorders, especially
seasonal affective disorder
Seasonal affective disorder (SAD) is a mood disorder subset, in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year.
Common symptoms include sleeping too much, having li ...
(SAD) and circadian rhythm sleep-wake disorders. Treating skin conditions such as neurodermatitis, psoriasis,
acne vulgaris
Acne, also known as ''acne vulgaris'', is a long-term skin condition that occurs when dead skin cells and oil from the skin clog hair follicles. Typical features of the condition include blackheads or whiteheads, pimples, oily skin, and po ...
, and
eczema
Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can ...
with ultraviolet light is called
ultraviolet light therapy
Ultraviolet light therapy or ultraviolet phototherapy is a form of treatment for certain skin disorders including atopic skin disorder and vitiligo when used with psoralen to form the PUVA treatment. It consists of irradiation of the patient wi ...
.
Medical uses
Nutrient deficiency
Vitamin D deficiency
Exposure to light at specific wavelengths of
Ultraviolet B
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
(abbreviated as UV-B or UVB) enables the body to produce
vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
to treat
vitamin D deficiency
Vitamin D deficiency or hypovitaminosis D is a vitamin D level that is below normal. It most commonly occurs in people when they have inadequate exposure to sunlight, particularly sunlight with adequate ultraviolet B rays (UVB). Vitamin D defic ...
.
Skin conditions
![Blue Light acne phototherapy iClear](https://upload.wikimedia.org/wikipedia/commons/2/29/Blue_Light_acne_phototherapy_iClear.jpg)
Light therapy treatments for the skin usually involve exposure to
ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
. The exposures can be to a small area of the skin or over the whole body surface, as in a
tanning bed
Indoor tanning involves using a device that emits ultraviolet radiation to produce a cosmetic tan. Typically found in tanning salons, gyms, spas, hotels, and sporting facilities, and less often in private residences, the most common device is a ho ...
. The most common treatment is with
narrowband
Narrowband signals are signals that occupy a narrow range of frequencies or that have a small fractional bandwidth. In the audio spectrum, narrowband sounds are sounds that occupy a narrow range of frequencies. In telephony, narrowband is usua ...
UVB, which has a wavelength of approximately 311–313 nanometers. Full body phototherapy can be delivered at a doctor's office or at home using a large high-power UVB booth. Tanning beds, however, generate mostly UVA light, and only 4% to 10% of tanning-bed light is in the UVB spectrum.
Acne vulgaris
evidence for light therapy and lasers in the treatment of acne vulgaris was not sufficient to recommend them. There is moderate evidence for the efficacy of blue and blue-red light therapies in treating mild acne, but most studies are of low quality. While light therapy appears to provide short-term benefit, there is a lack of long-term outcome data or data in those with severe acne.
Atopic dermatitis
Light therapy is considered one of the best monotherapy treatments for
atopic dermatitis
Atopic dermatitis (AD), also known as atopic eczema, is a long-term type of inflammation of the skin (dermatitis). It results in puritis, itchy, red, swollen, and cracked skin. Clear fluid may come from the affected areas, which often thickens o ...
(AD) when applied to patients who have not responded to traditional topical treatments. The therapy offers a wide range of options: UVA1 for acute AD, NB-UVB for chronic AD, and
balneophototherapy have proven their efficacy. Patients tolerate the therapy safely but, as in any therapy, there are potential adverse effects and care must be taken in its application, particularly to children.
Cancer
According to the
American Cancer Society
The American Cancer Society (ACS) is a nationwide voluntary health organization dedicated to eliminating cancer. Established in 1913, the society is organized into six geographical regions of both medical and lay volunteers operating in more than ...
, there is some evidence that ultraviolet light therapy may be effective in helping treat certain kinds of
skin cancer
Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
, and ultraviolet
blood irradiation therapy
Blood irradiation therapy is an alternative medical procedure in which the blood is exposed to low level light (often laser light) for therapeutic reasons. The practice was originally developed in the United States, but most recent research on i ...
is established for this application. However, alternative uses of light for cancer treatment – light box therapy and
colored light therapy – are not supported by evidence.
Photodynamic therapy
Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance, used in conjunction with molecular oxygen to elicit cell death (phototoxicity).
PDT is popularly used in treating acne. It is used cl ...
(often with red light) is used to treat certain superficial non-melanoma skin cancers.
Psoriasis
For
psoriasis
Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by raised areas of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete ...
, UVB phototherapy has been shown to be effective. A feature of psoriasis is localized
inflammation
Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
mediated by 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 ...
.
Ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
radiation is known to suppress 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 ...
and reduce inflammatory responses. Light therapy for skin conditions like psoriasis usually use 313 nanometer UVB though it may use UVA (315–400 nm wavelength) or a broader spectrum UVB (280–315 nm wavelength). UVA combined with
psoralen
Psoralen (also called psoralene) is the parent compound in a family of naturally occurring organic compounds known as the linear furanocoumarins. It is structurally related to coumarin by the addition of a fused furan ring, and may be considered ...
, a drug taken orally, is known as
PUVA
PUVA (psoralen and UVA) is an ultraviolet light therapy treatment for skin diseases: eczema, psoriasis, graft-versus-host disease, vitiligo, mycosis fungoides, large plaque parapsoriasis, and cutaneous T-cell lymphoma, using the sensitizing e ...
treatment. In UVB phototherapy the exposure time is very short, seconds to minutes depending on intensity of lamps and the person's skin pigment and sensitivity.
Vitiligo
About 1% of the human population has
vitiligo
Vitiligo is a disorder that causes the skin to lose its color. Specific causes are unknown but studies suggest a link to immune system changes.
Signs and symptoms
The only sign of vitiligo is the presence of pale patchy areas of depigmen ...
which causes painless distinct light-colored patches of the skin on the face, hands, and legs. Phototherapy is an effective treatment because it forces skin cells to manufacture
melanin
Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
to protect the body from UV damage. Prescribed treatment is generally 3 times a week in a clinic or daily at home. About 1 month usually results in re-pigmentation in the face and neck, and 2–4 months in the hands and legs. Narrowband UVB is more suitable to the face and neck and PUVA is more effective at the hands and legs.
Wound healing
Low level laser therapy
Low-level laser therapy (LLLT), cold laser therapy, or photobiomodulation (PBM) is a form of medicine that applies low-level (low-power) lasers or light-emitting diodes (LEDs) to the surface of the body. Whereas high-power lasers are used in la ...
has been studied as a potential treatment for
chronic wound A chronic wound is a wound that does not heal in an orderly set of stages and in a predictable amount of time the way most wounds do; wounds that do not heal within three months are often considered chronic.
Chronic wounds seem to be detained in on ...
s, and higher-power lasers have sometimes been successfully used to close acute wounds as an alternative to
stitching.
However, and due to inconsistent results and the low quality of extant research, reviews in the scientific literature have not supported its widespread application.
Other skin conditions
Some types of phototherapy may be effective in the treatment of
polymorphous light eruption
Polymorphous light eruption (PLE) presents with itchy red small bumps on sun-exposed skin, particularly face, neck, forearms and legs. It generally appears 30 minutes to a few hours after sun exposure and may last between one and 14 days. The b ...
,
cutaneous T-cell lymphoma and
lichen planus
Lichen planus (LP) is a chronic inflammatory and immune-mediated disease that affects the skin, nails, hair, and mucous membranes. It is not an actual lichen, and is only named that because it looks like one. It is characterized by polygonal, fla ...
. Narrowband UVB between 311 and 313 nanometers is the most common treatment.
Retinal conditions
There is preliminary evidence that light therapy is an effective treatment for
diabetic retinopathy
Diabetic retinopathy (also known as diabetic eye disease), is a medical condition in which damage occurs to the retina due to diabetes mellitus. It is a leading cause of blindness in developed countries.
Diabetic retinopathy affects up to 80 perc ...
and
diabetic macular oedema.
Mood and sleep related
Seasonal affective disorder
The effectiveness of light therapy for treating
seasonal affective disorder
Seasonal affective disorder (SAD) is a mood disorder subset, in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year.
Common symptoms include sleeping too much, having li ...
(SAD) may be linked to the fact that light therapy makes up for lost
sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
exposure and resets the body's internal clock. Studies show that light therapy helps reduce the debilitating and depressive behaviors of SAD, such as excessive sleepiness and fatigue, with results lasting for at least 1 month. Light therapy is preferred over
antidepressant
Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness, hea ...
s in the treatment of SAD because it is a relatively safe and easy therapy.
Two methods of light therapy, bright light and dawn simulation, have similar success rates in the treatment of SAD.
It is possible that response to light therapy for SAD could be
season
A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and pol ...
dependent. Morning therapy has provided the best results because light in the early morning aids in regulating the
circadian rhythm
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
.
People affected by SAD have low levels of energy and have difficulty concentrating. They usually have a change in
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 ...
and experience trouble sleeping.
A 2007
systematic review
A systematic review is a Literature review, scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from publ ...
by the Swedish agency SBU found insufficient evidence that light therapy was able to alleviate symptoms of depression or seasonal affective disorder.
The report recommended that: "Approximately 100 participants are required to establish whether the therapy is moderately more effective than
placebo
A placebo ( ) is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills), inert injections (like Saline (medicine), saline), sham surgery, and other procedures.
In general ...
".
Although treatment in light therapy rooms was well established in Sweden, no satisfactory, controlled studies had been published on the subject.
This led to the closure of a number of clinics offering light therapy in Sweden.
A
Cochrane review conducted in 2019 states the evidence that light therapy's effectiveness as a treatment for the ''prevention'' of seasonal affective disorder is limited, although the risk of adverse effects are minimal. Therefore, the decision to use light therapy should be based on a person's preference of treatment.
Non-seasonal depression
Light therapy has also been suggested in the treatment of non-seasonal depression and other psychiatric mood disturbances, including
major depressive disorder
Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Introdu ...
,
bipolar disorder
Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last from days to weeks each. If the elevated mood is severe or associated with ...
and
postpartum depression
Postpartum depression (PPD), also called postnatal depression, is a type of mood disorder associated with childbirth, which can affect both sexes. Symptoms may include extreme sadness, low energy, anxiety, crying episodes, irritability, and cha ...
. A meta-analysis by the
Cochrane Collaboration
Cochrane (previously known as the Cochrane Collaboration) is a British international charitable organisation formed to organise medical research findings to facilitate evidence-based choices about health interventions involving health profess ...
concluded that "for patients suffering from non-seasonal depression, light therapy offers modest though promising antidepressive efficacy." A 2008
systematic review
A systematic review is a Literature review, scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from publ ...
concluded that "overall, bright light therapy is an excellent candidate for inclusion into the therapeutic inventory available for the treatment of nonseasonal depression today, as adjuvant therapy to antidepressant medication, or eventually as stand-alone treatment for specific subgroups of depressed patients." A 2015 review found that supporting evidence for light therapy was limited due to serious
methodological
In its most common sense, methodology is the study of research methods. However, the term can also refer to the methods themselves or to the philosophical discussion of associated background assumptions. A method is a structured procedure for bri ...
flaws.
A 2016 meta-analysis showed that bright light therapy appeared to be efficacious, particularly when administered for 2–5 weeks' duration and as monotherapy.
Chronic circadian rhythm sleep disorders (CRSD)
In the management of
circadian rhythm disorders such as
delayed sleep phase disorder
Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is a delaying of a person's circadian rhythm (biological clock) compared to those of societal norms. The diso ...
(DSPD), the timing of light exposure is critical. Light exposure administered to the eyes before or after the
nadir
The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
The direc ...
of the core body temperature rhythm can affect the
phase response curve
A phase response curve (PRC) illustrates the transient change ( phase response) in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received. PRCs are used in various fields; examples of biol ...
. Use upon awakening may also be effective for
non-24-hour sleep–wake disorder
Non-24-hour sleep–wake disorder (non-24 or N24SWD) is one of several chronic circadian rhythm sleep disorders (CRSDs). It is defined as a "chronic steady pattern comprising ..daily delays in sleep onset and wake times in an individual livin ...
. Some users have reported success with lights that turn on shortly ''before'' awakening (
dawn simulation
Dawn simulation is a technique that involves timing lights, often called wake up lights, sunrise alarm clock or natural light alarm clocks, in the bedroom to come on gradually, over a period of 30 minutes to 2 hours, before awakening to simulate da ...
). Evening use is recommended for people with
advanced sleep phase disorder
Advanced Sleep Phase Disorder (ASPD), also known as the advanced sleep-phase type (ASPT) of circadian rhythm sleep disorder, is a condition that is characterized by a recurrent pattern of early evening (e.g. 7-9 PM) sleepiness and very early morn ...
. Some, but not all, totally
blind people whose
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
e are intact, may benefit from light therapy.
Circadian rhythm sleep disorders and jet lag
=Situational CRSD
=
Light therapy has been tested for individuals with
shift work sleep disorder and for
jet lag
Jet lag is a physiological condition that results from alterations to the body's circadian rhythms caused by rapid long-distance trans-meridian (east–west or west–east) travel. For example, someone flying from New York to London, i.e. from ...
.
= Sleep disorder in Parkinson's disease
=
Light therapy has been trialed in treating sleep disorders experienced by patients with
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
.
= Sleep disorder in Alzheimer's disease
=
Studies have shown that daytime and evening light therapy for nursing home patients with
Alzheimer's disease
Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
, who often struggle with agitation and fragmented wake/rest cycles effectively led to more consolidated sleep and an increase in circadian rhythm stability.
Neonatal jaundice (Postnatal Jaundice)
![Jaundice phototherapy](https://upload.wikimedia.org/wikipedia/commons/d/d9/Jaundice_phototherapy.jpg)
Light therapy is used to treat cases of
neonatal jaundice
Neonatal jaundice is a yellowish discoloration of the white part of the eyes and skin in a newborn baby due to high bilirubin levels. Other symptoms may include excess sleepiness or poor feeding. Complications may include seizures, cerebral pal ...
.
Bilirubin
Bilirubin (BR) (Latin for "red bile") is a red-orange compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the ...
, a yellow pigment normally formed in the
liver
The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
during the breakdown of old red blood cells, cannot always be effectively cleared by a neonate's liver causing neonatal jaundice. Accumulation of excess bilirubin can cause
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
damage, and so this buildup of bilirubin must be treated. Phototherapy uses the energy from light to isomerize the bilirubin and consequently transform it into compounds that the newborn can excrete via urine and stools. Bilirubin is most successful absorbing light in the blue region of the visible light spectrum, which falls between 460 and 490 nm.
Therefore, light therapy technologies that utilize these blue wavelengths are the most successful at isomerizing bilirubin.
Techniques
Photodynamic therapy
Photodynamic therapy is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells.
One of the treatments is using blue light with
aminolevulinic acid for the treatment of
actinic keratosis
Actinic keratosis (AK), sometimes called solar keratosis or senile keratosis, is a pre-cancerous area of thick, scaly, or crusty skin.Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. . Actinic k ...
. This is not a U.S. FDA-approved treatment for acne vulgaris.
Light boxes
![Light therapy lamp and sunlight](https://upload.wikimedia.org/wikipedia/commons/0/0c/Light_therapy_lamp_and_sunlight.jpg)
The production of the hormone
melatonin, a sleep regulator, is inhibited by light and permitted by darkness as registered by
photosensitive ganglion cell
Intrinsically photosensitive retinal ganglion cells (ipRGCs), also called photosensitive retinal ganglion cells (pRGC), or melanopsin-containing retinal ganglion cells (mRGCs), are a type of neuron in the retina of the mammalian eye. The presence ...
s in the
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
. To some degree, the reverse is true for
serotonin
Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...
, which has been linked to
mood disorder
A mood disorder, also known as an affective disorder, is any of a group of conditions of mental and behavioral disorder where a disturbance in the person's mood is the main underlying feature. The classification is in the ''Diagnostic and Stat ...
s. Hence, for the purpose of manipulating melatonin levels or timing, light boxes providing very specific types of artificial
illumination to the retina of the eye are effective.
Light therapy uses either a light box which emits up to 10,000
lux of light at a specified distance, much brighter than a customary lamp, or a lower intensity of specific wavelengths of light from the blue (460
nm) to the green (525 nm) areas of the
visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...
. A 1995 study showed that green light therapy at doses of 350 lux produces melatonin suppression and phase shifts equivalent to 10,000 lux white light therapy, but another study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination, because of a possible involvement of the
cones
A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex.
A cone is formed by a set of line segments, half-lines, or lines conn ...
in melatonin suppression.
Risks and complications
Ultraviolet
Ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
light causes progressive damage to human skin and
erythema
Erythema (from the Greek , meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not assoc ...
even from small doses.
This is mediated by
genetic damage
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitos ...
,
collagen
Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
damage, as well as destruction of
vitamin A
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...
and
vitamin C
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) an ...
in the skin and
free radical
A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing.
Ageing
Ailments of unknown cause
Biogerontology
Biological processes
Causes of death
Cellular processes
Gerontology
Life extension
Metabo ...
generation. Ultraviolet light is also known to be a factor in formation of
cataract
A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
s. Ultraviolet radiation exposure is strongly linked to incidence of
skin cancer
Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
.
Visible light
Optical radiation
Optical radiation is part of the electromagnetic spectrum. It is subdivided into ultraviolet radiation (UV), the spectrum of light visible for man (VIS) and infrared radiation
Infrared (IR), sometimes called infrared light, is electromagnetic ...
of any kind with enough intensity can cause damage to the eyes and skin including photoconjunctivitis and
photokeratitis
Photokeratitis or ultraviolet keratitis is a painful eye condition caused by exposure of insufficiently protected eyes to the ultraviolet (UV) rays from either natural (e.g. intense sunlight) or artificial (e.g. the electric arc during welding) ...
. Researchers have questioned whether limiting blue light exposure could reduce the risk of
age-related macular degeneration
Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...
. According to the
American Academy of Ophthalmology, there is no scientific evidence showing that exposure to blue light emitting devices result in eye damage. According to
Harriet Hall
Harriet A. Hall (born July 2, 1945) is a U.S. retired family physician, former U.S. Air Force flight surgeon and skeptic who writes about alternative medicine and quackery for ''Skeptic'' and ''Skeptical Inquirer''. She writes under the name T ...
, blue light exposure is reported to suppress the production of
melatonin, which affects our body's
circadian rhythm
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
and can decrease sleep quality. It is reported that bright light therapy may activate the production of reproductive
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
s, such as
testosterone
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
,
luteinizing hormone
Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) ...
,
follicle-stimulating hormone
Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, pubertal maturation, an ...
, and
estradiol
Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles. Estradiol is responsible for the development of f ...
.
Modern phototherapy lamps used in the treatment of seasonal affective disorder and
sleep disorder
A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are test ...
s either filter out or do not emit ultraviolet light and are considered safe and effective for the intended purpose, as long as
photosensitizing drugs are not being taken at the same time and in the absence of any existing eye conditions. Light therapy is a mood altering treatment, and just as with drug treatments, there is a possibility of triggering a
manic state
Mania, also known as manic syndrome, is a mental and behavioral disorder defined as a state of abnormally elevated arousal, affect, and energy level, or "a state of heightened overall activation with enhanced affective expression together wit ...
from a
depressive state, causing
anxiety
Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...
and other
side effect
In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
s. While these side effects are usually controllable, it is recommended that patients undertake light therapy under the supervision of an experienced clinician, rather than attempting to self-medicate.
Contraindication
In medicine, a contraindication is a condition that serves as a reason not to take a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a reason to use a certain tre ...
s to light therapy for seasonal affective disorder include conditions that might render the eyes more vulnerable to
phototoxicity
Phototoxicity, also called photoirritation, is a chemically induced skin irritation, requiring light, that does not involve the immune system. It is a type of photosensitivity.
The skin response resembles an exaggerated sunburn. The involved chemi ...
, tendency toward mania, photosensitive skin conditions, or use of a photosensitizing herb (such as
St. John's wort
''Hypericum perforatum'', known as St. John's wort, is a flowering plant in the family Hypericaceae and the type species of the genus ''Hypericum''.
Possibly a hybrid between ''Hypericum maculatum, H. maculatum'' and ''Hypericum attenuatum, H. ...
) or medication. Patients with
porphyria
Porphyria is a group of liver disorders in which substances called porphyrins build up in the body, negatively affecting the skin or nervous system. The types that affect the nervous system are also known as acute porphyria, as symptoms are ra ...
should avoid most forms of light therapy. Patients on certain drugs such as
methotrexate
Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. Types of cancers it is used for include breast cancer, leuke ...
or
chloroquine
Chloroquine is a medication primarily used to prevent and treat malaria in areas where malaria remains sensitive to its effects. Certain types of malaria, resistant strains, and complicated cases typically require different or additional medi ...
should use caution with light therapy as there is a chance that these drugs could cause porphyria.
Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness,
headache
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 ...
, eye irritation and
nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
. Some non-depressive physical complaints, such as poor vision and skin rash or irritation, may improve with light therapy.
History
![Sun therapy at Alton Hospital Wellcome L0074520](https://upload.wikimedia.org/wikipedia/commons/2/22/Sun_therapy_at_Alton_Hospital_Wellcome_L0074520.jpg)
Many ancient cultures practiced various forms of heliotherapy, including people of
Ancient Greece
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...
,
Ancient Egypt, and
Ancient Rome
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 B ...
. The
Inca
The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, (Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The admin ...
,
Assyria
Assyria (Neo-Assyrian cuneiform: , romanized: ''māt Aššur''; syc, ܐܬܘܪ, ʾāthor) was a major ancient Mesopotamian civilization which existed as a city-state at times controlling regional territories in the indigenous lands of the A ...
n and early
Germanic peoples
The Germanic peoples were historical groups of people that once occupied Central Europe and Scandinavia during antiquity and into the early Middle Ages. Since the 19th century, they have traditionally been defined by the use of ancient and ear ...
also worshipped the sun as a health bringing
deity
A deity or god is a supernatural being who is considered divine or sacred. The ''Oxford Dictionary of English'' defines deity as a god or goddess, or anything revered as divine. C. Scott Littleton defines a deity as "a being with powers greate ...
. Indian medical literature dating to 1500 BCE describes a treatment combining
herb
In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...
s with natural sunlight to treat non-pigmented skin areas.
Buddhist literature
Buddhist texts are those religious texts which belong to the Buddhist tradition. The earliest Buddhist texts were not committed to writing until some centuries after the death of Gautama Buddha. The oldest surviving Buddhist manuscripts a ...
from about 200 CE and 10th-century Chinese documents make similar references.
The
Faroese physician
A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through th ...
Niels Finsen
Niels Ryberg Finsen (15 December 1860 – 24 September 1904) was a Faroese- Icelandic physician and scientist. In 1903, he was awarded the Nobel Prize in Medicine and Physiology "in recognition of his contribution to the treatment of diseases, e ...
is believed to be the father of modern phototherapy. He developed the first artificial light source for this purpose. Finsen used short wavelength light to treat
lupus vulgaris
Lupus vulgaris (also known as tuberculosis luposa) are painful cutaneous tuberculosis skin lesions with nodular appearance, most often on the face around the nose, eyelids, lips, cheeks, ears and neck. It is the most common ''Mycobacterium tuberc ...
, a skin infection caused by ''
Mycobacterium tuberculosis
''Mycobacterium tuberculosis'' (M. tb) is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, ''M. tuberculosis'' has an unusual, waxy coating on its c ...
''. He thought that the beneficial effect was due to ultraviolet light killing the
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
, but recent studies showed that his lens and filter system did not allow such short wavelengths to pass through, leading instead to the conclusion that light of approximately 400 nanometers generated
reactive oxygen
In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen.
The reduction of molecular oxygen () ...
that would kill the bacteria. Finsen also used red light to treat
smallpox
Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) c ...
lesions. He received the
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
in 1903. Scientific evidence for some of his treatments is lacking, and later eradication of smallpox and development of
antibiotics
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention o ...
for
tuberculosis
Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
rendered light therapy obsolete for these diseases. In the early 20th-century light therapy was promoted by
Auguste Rollier and
John Harvey Kellogg
John Harvey Kellogg (February 26, 1852 – December 14, 1943) was an American medical doctor, nutritionist, inventor, health activist, eugenicist, and businessman. He was the director of the Battle Creek Sanitarium in Battle Creek, Michigan. The ...
. In 1924,
Caleb Saleeby founded
The Sunlight League
The Sunlight League was founded in England in 1924 by C. W. Saleeby. Its aim was: "to point to the light of day, to advocate its use for the cure of disease—"helio-therapy"; and, immeasurably better, for preventive medicine and constructive hea ...
.
From the late nineteenth century until the early 1930s, light therapy was considered an effective and mainstream medical therapy in the UK for conditions such as varicose ulcer, 'sickly children' and a wide range of other conditions. Controlled trials by the medical scientist
Dora Colebrook, supported by the Medical Research Council, indicated that light therapy was not effective for such a wide range of conditions.
See also
*
Blood irradiation therapy
Blood irradiation therapy is an alternative medical procedure in which the blood is exposed to low level light (often laser light) for therapeutic reasons. The practice was originally developed in the United States, but most recent research on i ...
*
Chromotherapy
Chromotherapy, sometimes called color therapy, colorology or cromatherapy, is an alternative medicine method that is considered pseudoscience and quackery. Chromotherapists claim to be able to use light in the form of color to balance "energy" l ...
*
Crib A'Glow
Crib A'Glow is a portable solar-powered phototherapy unit that uses blue LED lights to treat infants with jaundice. The device was invented by Virtue Oboro, a visual designer and mother whose newborn son had developed jaundice. Crib A'Glow has won ...
*
Free-running sleep Free-running sleep is a rare sleep pattern whereby the sleep schedule of a person shifts later every day. It occurs as the sleep disorder non-24-hour sleep–wake disorder or artificially as part of experiments used in the study of circadian and ot ...
*
Low level laser therapy
Low-level laser therapy (LLLT), cold laser therapy, or photobiomodulation (PBM) is a form of medicine that applies low-level (low-power) lasers or light-emitting diodes (LEDs) to the surface of the body. Whereas high-power lasers are used in la ...
*
Photodynamic therapy
Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance, used in conjunction with molecular oxygen to elicit cell death (phototoxicity).
PDT is popularly used in treating acne. It is used cl ...
*
Sun tanning
Sun tanning or tanning is the process whereby skin color is darkened or tanned. It is most often a result of exposure to ultraviolet (UV) radiation from sunlight or from artificial sources, such as a tanning lamp found in indoor tanning beds. ...
*
UV-B lamps
References
Natural Light Therapy Significantly accelerates Antidepressants Response.
The Canadian Review of Affective Disorder, vol. 5, No 4, Autumn 1995.
Khaled Mohamed, M.D.: Gregory Asnis, M.D.
External links
Our Friend, the Sun: Images of Light Therapeutics from the Osler Library Collection, c. 1901–1944 Digital exhibition by the
Osler Library of the History of Medicine
The Osler Library, a branch of the McGill University Library and part of ROAAr since 2016, is Canada's foremost scholarly resource for the history of medicine, and one of the most important libraries of its type in North America. It is located i ...
,
McGill University
McGill University (french: link=no, Université McGill) is an English-language public research university located in Montreal, Quebec, Canada. Founded in 1821 by royal charter granted by King George IV,Frost, Stanley Brice. ''McGill Universit ...
{{Authority control
Psoriasis
Circadian rhythm
Acne treatments
Treatment of bipolar disorder
Neonatology