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 UV rays. You may develop a rash, blisters, or scaly patches. Exposure levels and reactions differ for every person. Several factors can make your skin sensitive to UV rays, including having an inherited tendency to photosensitivity, taking certain medications, or being exposed to plants in the Apiaceal or Umbelliferae family, including weeds and edible plants, such as hogweed, cowbane, carrot, parsnip, dill, fennel, celery, and anise.

• 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 have several causes, including:

• Diseases, such as lupus or eczema, that also make skin sensitive to light
• Genetic or metabolic factors (inherited diseases or conditions, such as pellagra, caused by lack of niacin, vitamin B-3)
• Diseases, such as polymorphic light eruptions, characterized by sensitivity to sunlight
• Reactions to chemicals and medications.

In reaction to UV rays, certain chemicals and drugs can cause sunburn, an eczema-like reaction, or hives. 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
• Lavender

• 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 (the frequency of photodermatitis in African Americans is similar to that in caucasions)
• 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 between 11 a.m. - 2 p.m. (50% of UV radiation is emitted during this time).

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

Prevention

These measures may help prevent photodermatitis:

• Limit sun exposure, 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 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 Nutrition section).

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 leads to photosensitivity. Other nutrients, particularly antioxidants and flavonoids, may help protect skin against sun damage in healthy people. Antioxidants help protect skin from damage. Recent studies suggest that antioxidants, especially beta-carotene, may help lessen the symptoms of photodermatitis.

Some supplements and herbs may be beneficial for some people but cause side effects or undesired drug interactions in others. Always tell your health care providers about any supplement or CAM therapy you are using or considering using.

You may address nutritional deficiencies with the following supplements:

• A multivitamin daily, containing the antioxidant vitamins A, C, E, D, B-complex vitamins, and trace minerals such as magnesium, calcium, zinc, and selenium.
• B-complex vitamin, 1 tablet daily.
• Vitamin C, 1 - 6 gm daily, as an antioxidant. Vitamin C may interfere with vitamin B12, so take doses at least 2 hours apart. Lower the dose if diarrhea develops.
• Vitamin D, 200 - 400 I.U. daily.
• Alpha-lipoic acid, 25 - 50 mg twice daily, for antioxidant support. In people who have a Thiamine (vitamin B1) deficiency, taking Alpha-lipoic acid can cause dangerous complications. 
• Omega-3 fatty acids, such as flaxseed and fish oils, 1 - 2 capsules or 1 - 2 tablespoonfuls oil daily. Omega-3 fatty acids can have a blood-thinning effect and may increase the blood-thinning action of certain medications, including warfarin (Coumadin), aspirin, and others. Speak with your physician.

Herbs

Herbs are generally available as standardized, dried extracts (pills, capsules, or tablets), teas, or tinctures/liquid extracts (alcohol extraction, unless otherwise noted). Mix liquid extracts with favorite beverage. Dose for teas is 1 - 2 heaping teaspoonfuls/cup water steeped for 10 - 15 minutes (roots need longer).

• Rhodiola (Rhodiola rosea) standardized extract, 150 - 300 mg 1 - 3 times daily, for radiation protection. Rhodiola is an "adaptogen" and helps the body adapt to stress.
• Astragalus (Astragalus membranaceus) standardized extract, 250 - 500 mg 3 - 4 times daily, for radiation protection. Astragalus can interfere with lithium, among other medications.  Speak with your physician.

Herbs to avoid

Some herbs can cause photodermatitis, including:

• 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. The 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.

Afaq F, Malik A, Syed D, Maes D, Matsui M, Mukhtar H. Pomegranate fruit extract modulates UVB-mediated phosphorylation of mitogen activated protein kinases and activation of nuclear factor kappa B in normal human epidermal keratinocytes. Photochem Photobiol. 2005 Jan-Feb;81(1):38-45

Auerbach: Wilderness Medicine, 6th ed. St. Louis, MO: Mosby; 2011.

Goldman L, Bennett JC. Cecil Textbook of Medicine. 21st ed. Philadelphia, Pa: W.B. Saunders; 2000:2295-2296.

Heinrich U, Neukam K, Tronnier H, Sies H, Stahl W. Long-term ingestion of high flavanol cocoa provides photoprotection against UV-induced erythema and improves skin condition in women. J Nutr. 2006 Jun;136(6):1565-9

Jindal N, Sharma NL, Mahajan VK, Shanker V, Tegta GR, Verma GK. Evaluation of photopatch test allergens for Indian patients of photodermatitis: preliminary results. Indian J Dermatol Venereol Leprol. 2011: 77(2):148-55.

Katiyar SK, Afaq F, Perez A, Mukhtar H. Green tea polyphenol (-)-epigallocatechin-3-gallate treatment of human skin inhibits ultraviolet radiation-induced oxidative stress. Carcinogenesis. 2001 Feb;22(2):287-94.

Kerr H, Lim H. Photodermatoses in African Americans: A retrospectivce analysis of 135 patients over a 7-year period. J of the Amer Acad of Derm. 2007;57(4).

Morganti P. The photoprotective activity of nutraceuticals. Clin Dermatol. 2009; 27(2):166-74.

Sasseville D. Clinical Patterns of Phytodermatitis. Dermatologic Clinics. 2009;27(3).

Stahl W, Heinrich U, Jungmann H, Sies H, Tronnier H. Carotenoids and carotenoids plus vitamin E protect against ultraviolet light-induced erythema in humans. Am J Clin Nutr. 2000;71(3):795-798.

Tierney LM, McPhee SJ, Papadakis MA. Current Medical Diagnosis and Treatment 2000. New York, NY: Lange Medical Books/McGraw-Hill; 2000:177-178.

Wu PA, James WD. Lavender. Dermatitis. 2011; 22(6):344-7.