Photodermatitis is an abnormal skin reaction to sunlight, or more specifically to ultraviolet (UV) rays. It can be acute (sudden) or chronic (ongoing). Photodermatitis occurs when your immune system reacts to the UV rays. You may develop a rash, blisters, or scaly patches. How much exposure to sunlight will cause such a reaction is different for every person. Several factors can make your skin sensitive to light UV rays, including an inherited tendency to photosensitivity or taking certain medications.

• Itchy bumps, blisters, or raised areas
• Lesions that resemble eczema
• Hyperpigmentation (dark patches on your skin)
• Outbreaks in areas of skin exposed to light
• Pain, redness, and swelling
• Chills, headache, fever, and nausea
• Long-term effects include thickening and scarring of the skin and an increased risk of skin cancer, if the cause is genetic.

Photodermatitis can be caused by certain diseases, such as lupus or eczema, that also make skin sensitive to light; by genetic or metabolic factors (inherited diseases or conditions such as pellagra, caused by lack of niacin, vitamin B-3); by diseases such as polymorphic light eruptions, which is characterized by sensitivity to sunlight; and by reactions to chemicals and medications. Certain chemicals and drugs can cause sunburn, an eczema-like reaction, or hives in reaction to UV rays. The reaction may be related to an allergy or it may be a direct toxic effect from the substance. Below are examples of substances or circumstances that may trigger one or the other type of reaction:

Direct toxic effect:

• Antibiotics, such as tetracycline and sulfonamides
• Antifungals, such as griseofulvin
• Coal tar derivatives and psoralens, used topically for psoriasis
• Retinoids, such as tretinoin and medications containing retinoic acid, used for acne
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Chemotherapy agents
• Sulfonylureas, oral medications used for diabetes
• Antimalarial drugs, such as quinine and other medications, used to treat malaria
• Diuretics
• Antidepressants, such as the tricyclics, used for depression
• Antipsychotics, such as phenothiazines
• Anti-anxiety medications, such as benzodiazepines

Allergic reactions:

• Fragrances
• Sunscreens with PABA
• Industrial cleaners that contain salicylanilide

• People with fair to light skin -- or those with red or blond hair -- and green or blue eyes tend to be most sensitive, regardless of their racial or ethnic background. This is categorized as skin type I.
• People with lupus, porphyria, or polymorphous light eruptions
• Exposure to UV rays for 30 minutes to several hours increases risk (especially in spring and summer), as does exposure during 11 a.m. to 2 p.m. (50% of UV radiation is emitted during this time).

A physical exam and a detailed history of exposure to chemicals and drugs (see section titled What Causes It?) and UV rays are important for diagnosis. Your health care provider may order blood and urine tests to detect any related diseases. Allergy tests may help identify substances that trigger or worsen the condition.

Prevention

These measures may help prevent photodermatitis:

• Limit skin exposure to sun, especially intense midday sun.
• Use PABA-free sunscreens that protect against UVA and have a sun protection factor (SPF) of 30 - 50.
• Cover up with a long-sleeved shirt, long pants, and a wide-brimmed hat.
• Beware of using any product that causes sun sensitivity. (If you are already taking a prescription medication, however, do not stop taking it without consulting your health care provider.)
• Do not use a tanning device (such as a tanning lamp or bed).

Treatment Plan

For blisters or weepy eruptions, apply cool, wet dressings. With certain types of photodermatitis, doctors may actually use phototherapy (controlled exposure to light for treatment purposes) to desensitize the skin or to help control symptoms.

Drug Therapies

For extremely sun-sensitive patients, doctors may prescribe azathioprine to suppress the immune system. Short-term use of glucocorticoids may help control eruptions. For those who cannot be treated with phototherapy, doctors may prescribe hydroxychloroquine, thalidomide, beta-carotene, or nicotinamide (see section entitled Nutrition for details regarding the latter two). Note: Thalidomide causes severe birth defects and should never be used by women who are pregnant or wish to become pregnant.

Complementary and Alternative Therapies

Nutrition and Supplements

If you don't get enough of some nutrients, your skin can become sensitive to sunlight. Pellagra, for example, is caused by a niacin deficiency and causes photosensitivity. Other nutrients, particularly antioxidants and flavonoids, may help protect skin against sun damage in healthy people. Antioxidants help remove free radicals, harmful by-products that result from cells' use and generation of energy. Free radicals are linked to skin damage. Recent studies suggest that antioxidants, especially beta-carotene, may help lessen the symptoms of photodermatitis.

Antioxidants

• Beta-carotene and other carotenoids (up to 300 IU per day for beta-carotene) -- Beta-carotene is often used as a standard treatment for photodermatitis, although studies have been mixed. In one trial, though, 20 healthy subjects received either carotenoids alone, mainly from beta-carotene, or carotenoids plus vitamin E. Both groups improved significantly, but vitamin E did not appear to add any benefits. Scientists think the protective effect of beta-carotene comes from its antioxidant effect, so it's possible other antioxidants may also help protect skin from damage.
• Vitamin B3 (1 g three times per day) -- Nicotinamide (a form of niacin, or vitamin B3) may make a photosensitive reaction less likely. In a pilot study, it reduced reactions among people with polymorphous light eruptions. Vitamin B3 is an antioxidant, so it may be providing protection in the same way other antioxidants might. You should take this high a dose of vitamin B3 only under a doctor's supervision because of the risk of side effects such as flushing and liver damage.
• Vitamin B6 (100 mg per day for 3 months) -- Some case reports suggest that vitamin B6 can help reduce the reaction to sunlight. You should take this high a dose of vitamin B6 only under a doctor's supervision, because of the risk of side effects.
• Vitamin C (1 - 3 g per day, lower dose if diarrhea develops) -- Vitamin C is an antioxidant, so it may provide some protection against photodermatitis. One small study showed an improvement in people with polymorphous light eruptions who took vitamin C.
• Vitamin E -- Vitamin E is also an antioxidant, and a few studies have shown that it can offer protection from photodermatitis when taken with vitamin C (but not alone). However, other studies have not found the same results.
• Vitamin D -- In animal studies, vitamin D helped protect against damage from UVB rays. It is not clear yet whether vitamin D supplements may protect humans in the same way.
• Flavonoids -- Some of these plant-based antioxidants may protect skin from sun damage in healthy people. In one recent study, German researchers found that drinking high-flavonol cocoa offered protection from the sun (the cocoa used was a special formulation that is not yet available commercially). In another study, pomegranate fruit extract helped protect skin cells in a test tube from UV light. It isn't yet known whether taking the extract would provide any benefit. However, adding a lot of fruits and vegetables to your diet in order to eat more flavonoids may help.

Other supplements

• Melatonin -- Applying melatonin topically seems to offer some protection against sunburn in healthy people, but it isn't known whether melatonin also lessens effects in people with photodermatitis.
• Omega-3 fatty acids or fish oil (10 g per day) -- In one small study, fish oil reduced symptoms in people with polymorphous light eruptions. It isn't known whether fish oil helps other kinds of photodermatitis, but it has other health benefits (reduced risk of heart disease, possible reduction in inflammation), so it can be helpful to add to your diet. Fish oil can increase the risk of bleeding, so do not take it if you also take blood-thinning medication.

Herbs

• Green tea (Camellia sinensis) -- Green tea has powerful antioxidant properties and may provide protection against reddening of the skin caused by UV light.
• Calendula (Calendula officinalis) -- Although there are no scientific studies, this herb has been used historically to treat sunburn. It is often used as a homeopathic remedy for that reason.

Herbs to avoid

Some herbs can cause photodermatitis.

• St. John's wort (Hypericum perforatum)
• Angelica seed or root (Angelica archangelica)
• Arnica (Arnica montana)
• Celery stems (Apium graveolens)
• Rue ( Rutae folium)
• Lime oil/peel ( Citrusaurantifolia)

Homeopathy

Few studies have examined the effectiveness of specific homeopathic remedies. A professional homeopath, however, may recommend one or more of the following treatments for photodermatitis based on his or her knowledge and clinical experience. Before prescribing a remedy, homeopaths take into account a person's constitutional type -- your physical, emotional, and intellectual makeup. An experienced homeopath assesses all of these factors when determining the most appropriate remedy for a particular individual.

• Aconitum napellus -- For a sudden rash, when the person feels anxious, frightened, and restless. Exposure to a cold, dry wind or sunlight may cause symptoms. If a rash breaks out suddenly and the person feels extremely anxious and apprehensive, this remedy may be indicated. Exposure to sunlight, or being out on a cold dry windy day, may precipitate symptoms. The rash may feel numb or itch, and stimulants may reduce the itching.
• Belladonna -- For a rash that comes on suddenly with a feeling of heat, and the face is flushed and burns. Belladonna is often used for sunstroke.
• Natrum carbonicum -- For a blistery rash that appears in patches. They person usually feels ill from exposure to the sun. They can be sensitive to changes in the weather and allergic to milk.
• Natrum muriaticum -- For those who feel tired after being in the sun, with headaches and a blotchy, itchy or burning rash. They may be thirsty and have a craving for salt. Symptoms tend to be worse in the morning.

Most photosensitivity reactions go away eventually and cause no permanent harm. However, symptoms can be serious when there is an underlying disease or when the exposure has been severe. Some photosensitivity reactions can continue for years after exposure ends.

Complications may include:

• Ongoing photosensitivity, resulting in chronic photodermatitis
• Hyperpigmentation or dark patches on the skin even after inflammation has ended
• Premature aging of the skin
• Squamous cell or basal cell skin cancer or melanoma

People who need steroids to treat photodermatitis must be monitored closely. In addition, anyone with a history of photodermatitis or photoreactivity should keep track of the frequency and duration of symptoms. This information can help determine appropriate treatment.

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