Chemical Photosensitivity: Be Careful in the Sun

by Food and Drug Administration (FDA)

Since childhood, my brother Blair always developed a dark tan without ever sunburning. Now a college soccer coach in Iowa, he is constantly outside practicing in the sun. Recently, Blair suffered a severe sunburn after only 45 minutes of sun exposure on a cool, partly sunny morning. Consulting his physician, he learned that the commonly prescribed colitis medication Azulfidine (sulfasalazine), which he was using at the time for a colon infection, was the cause of his problems.

Azulfidine is one of the many medications included in the Food and Drug Administration's most recent listing of medications that increase sensitivity to light and can cause a wide variety of health problems known as photosensitivity disorders. In some individuals, these medications can produce adverse effects when the person is exposed to sunlight and other types of ultraviolet (UV) light of an intensity or for a length of time that would not usually give the person problems. Some products are more likely to cause reactions than others. And not everyone who uses the products will be affected.

Photoreactions

Chemicals that produce a photoreaction (reaction with exposure to UV light) are called photoreactive agents or, more commonly, photosensitizers. After exposure to UV radiation either from natural sunlight or an artificial source such as tanning booths or even those "purple-lighted" mosquito zappers, these photosensitizers cause chemical changes that increase a person's sensitivity to light, causing the person to become photosensitized. Medications, food additives, and other products that contain photoreactive agents are called photosensitizing products.

FDA has also reported that photoreactive agents have been found in deodorants, antibacterial soaps, artificial sweeteners, fluorescent brightening agents for cellulose, nylon and wool fibers, naphthalene (mothballs), petroleum products, and in cadmium sulfide, a chemical injected into the skin during tattooing.

Photoreactive agents, such as Azulfidine, can cause both acute and chronic effects. Acute effects, from short-term exposure, include exaggerated sunburn-like skin conditions, eye burn, mild allergic reactions, hives, abnormal reddening of the skin, and eczema-like rashes with itching, swelling, blistering, oozing, and scaling of the skin. Chronic effects from long-term exposure include premature skin aging, stronger allergic reactions, cataracts, blood vessel damage, a weakened immune system, and skin cancer.

Widely used medications containing photoreactive agents include antihistamines, used in cold and allergy medicines; nonsteroidal anti-inflammatory drugs (NSAIDs), used to control pain and inflammation in arthritis; and antibiotics, including the tetracyclines and the sulfonamides, or "sulfa" drugs.

Sometimes this quality can be put to good medical use. For example, two well-known photoreactive chemicals, psoralens and coal-tar dye creams, are used together with UV lamps to treat psoriasis, a chronic skin condition characterized by bright red patches covered with silvery scales.

Pioneering Research

European scientists pioneered photosensitivity disorder research during the 1960s. In 1967, Danish researchers attributed strange skin lesions (any abnormal change on the skin) on women to perfumed soap. In 1967, British researchers discovered that sandalwood oil in sunscreens and facial cosmetics caused photoallergies and later reported that quindoxin, a food additive in animal feed also caused phototoxic erythemal skin patches on British farmers handling the feed.

Shortly thereafter, French scientists demonstrated that bergamot oil in sunscreens caused photosensitivity disorders. German researchers isolated photoreactive agents in colognes, perfumes and oral contraceptives.

In 1972, American scientists linked sunlight-activated aniline compounds (found in drugs, varnishes, perfumes, shoe polish, and vulcanized rubber) to hives and skin conditions such as dermatitis and dandruff.

Scientists were soon publishing laundry lists of photoreactive agents found in these substances as well as those in hair dyes, hair styling creams, and household items such as shoe polish and mothballs. Current research focuses on identifying what photoreactive agents are found in which medicinal products and how to control photosensitivity disorders.

Photosensitizers can cause either photoallergic or phototoxic reactions.

Photoallergies

In photoallergic reactions, which generally occur due to medications applied to the skin, UV light may structurally change the drug, causing the skin to produce antibodies. The result is an allergic reaction. Symptoms can appear within 20 seconds after sun exposure, producing eczema-like skin conditions that can spread to nonexposed parts of the body. But sometimes, photoallergic reactions can be delayed. For example, Yuko Kurumaji reported in the October 1991 issue of Contact Dermatitis that photoallergic sensitivity disorders to the topically applied NSAID Suprofen (not approved for use in the United States) took up to three months to develop.

Other regularly used products that can cause photoallergic reactions are cosmetics that contain musk ambrette, sandalwood oil, and bergamot oil; some quinolone antibacterials; and the over-the-counter (OTC) NSAID pain relievers Advil, Nuprin and Motrin (ibuprofen), and Aleve (naproxen sodium).

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.