Photosensitivity : Another Reason for UVA Skin Protection

We react normally to sun exposure by developing a tan or sunburn. But some of us react abnormally from photosensitivity. For instance, during the last two summers, I have broken out in a rash from the sun. My doctor said it is contact dermatitis, preciously, photocontact dermatitis. The allergen could even be a sunscreen ingredient.

UVA is a major trigger for photosensitivity. These rays can penetrate glass, so you’re exposed to UVA when you are near a window or driving your car. UVA penetrates deeper into skin than UVB and can cause premature aging. It can also contribute to skin cancer.

When UV radiation is absorbed by photosensitizer molecules, they in turn elicit a reaction in chromophores, molecules in the skin. The result is an abnormal skin reaction, such as a rash.

Photosensitizers can be either allergens or toxins. Phototoxins can be drugs, plants or coal tar derivatives. They cause sunburn like reactions, and are dose-dependent. Photoallergies elicit immune responses and tend to cause more severe skin reactions. Photoallergens can be drugs or topical agents and can spread beyond the sun exposed region of the skin. These molecules cause a rash like symptom. They are not dose-dependent.

Patients can react to sensitizers that originate outside or inside the body. Various drugs can cause photosensitivity. Cosmetics or other materials may contain potential photosensitizers that are deposited on the skin or given internally, whereas an immune disorder, such as lupus, can cause an abnormal reaction to the sun that originates inside the body.

Some organic sunscreen chemicals absorb UVA, UVB or both. Ingredients, such as octocrylene, protect against UVB. Ingredients, such as avobenzone (Parsol 1780) or a benzophenone (such as dioxybenzone, oxybenzone or sulisobenzone), protect partially against UVA. Some sunscreen ingredients provide physical sun protection that reflect or absorb UVA and/or UVB. These ingredients include zinc oxide and titanium dioxide. Most sunscreens contain a combination of active, as well as inactive ingredients.

“The physical blocking agents have not been reported to cause contact dermatitis, ” writes Daniel More, M.D., in his about.com column and who currently practices allergy and clinical immunology in Salinas, California and is an Assistant Clinical Professor in the Department of Family and Community Medicine at the UCSF School of Medicine. Also, studies have found that inorganic agents, such as zinc oxide, are photostable; they don’t degrade rapidly; however, organic agents tend to be less stable.

“Photostability depends not only on the sunscreen active ingredients but also on the inactive ingredients,” says Susan Cruz, spokesperson for the FDA. “You can compare two different sunscreens with the same active ingredients at the same concentration, and the sunscreens can have different SPF values,” says Susan Cruz, spokesperson for the FDA.

Sunscreen product labels don’t list the percentage of ingredients along with their synonyms. Example: Amyl dimethyl PABA (padimate A, isoamyl-p-N,N-dimethylaminobenzoate, Escalol 506, pentyldimethyl PABA). The FDA limits the percentage of sunscreen active ingredients. For example, zinc oxide is limited to 25%, Avobenzone, 3%.

FDA’s Office of Nonprescription Products within the Center for Drug Evaluation and Research (CDER) is developing UVA testing and labeling requirements for sunscreens. It is currently in final clearance. But in the meantime, avoid the sun between 10 and 4 when UV radiation is more intense, and use sunscreen properly by:

* checking the expiration date.
* applying sunscreen every 2 hours from sunrise to sunset all year round and every hour if you sweat or bathe since sunscreen wears of and loses effectiveness over time.
* applying sunscreen if you are near a window that gets sun or when you’re drying a car. Glass windows don’t block UV-A radiation.
* applying lip balm with broad spectrum sun protection.
* applying sunscreen when you plan to be in the shade since sun light is scattered in all direction, even under an umbrella.
* reapplying sunscreen after rubbing, such as towel drying. Rub the sunscreen in gently or you may rub it off.
* applying evenly a generous amount of sunscreen with broad spectrum sun protection, but don’t rub hard or you may rub it off. About an ounce is required to cover the entire body.

In addition to sunscreen, Cyndi Yag-Howard, M.D., a Florida dermatologist and spokesperson for the Skin Cancer Foundation, recommends that patients at high risk of skin cancer, which includes those who are photosensitive, wear under clothing a broad spectrum sunscreen with an SPF of at least 30, or purchase sun protective clothing that is labeled. And everyone should wear a wide brim hat and sunglasses that filter at least 98% of UV.