Men, women and children of all ethnic backgrounds and ages are affected by allergic reactions to the sun. The most common sun allergy, called Polymorphic Light Eruption, manifests itself as an itchy, painful rash, and it is the second most common sun-related skin problem after sunburns.
Hypersensitivity to sunlight can be triggered by a number of things, including sun exposure or even a chemical that was ingested or applied to the skin. In the case of sun exposure, sunlight can prompt an immune system response that inflames skin cells or skin proteins, creating an itchy rash. In the case of chemicals, both topical and ingested, the effect of sunlight on a certain ingredient can irritate the skin and make a person feel just generally ill.
Polymorphic Light Eruption (PLE), or Polymorphous Light Eruption (PMLE), describes a hypersensitivity to the sun's ultraviolet rays. Allergic reactions commonly occur at the first exposure to sunlight after a lengthy period of time, such as in the spring after a long winter. With repeated exposure to sunlight, the skin will decrease in sensitivity and rashes will become less severe, as long as the increase in exposure is reasonably gradual. There is also evidence of a hereditary form of PLE, the symptoms of which are more extreme than regular PLE and which occur prevalently in persons of American Indian ancestry. An allergic reaction to a chemical, whether applied topically or ingested, that has been exposed to sunlight is called a Photoallergic Eruption.
The most common symptoms of a sun allergy are red and itchy rashes or hives that appear on areas of skin which were exposed to sunlight approximately one to four days after the exposure occurred. The itchy areas may appear as bumps, blisters, bleeding below the skin or flat, or raised plaques. It is possible for the rash to spread to clothed areas if left untreated. Areas where symptoms commonly appear include the upper chest, the thighs, the torso, and any other body parts which are usually protected from the sun. In addition to hives or rashes, some affected persons experience chills, nausea and headaches.
In most cases an oral antihistamine will greatly reduce symptoms of a sun allergy. Topical treatments also provide relief for itching and include cooling gels, hydrocortisone creams, steroid creams, and anti-itch lotions. Prescription-strength products are the most effective. A person experiencing an allergic reaction should also avoid any further exposure, and the rash will usually disappear within a few days. Over time, if periods of exposure to sunlight are gradually lengthened, a person's skin will eventually accustom itself to the ultraviolet rays and sensitivity to sunlight will decrease. If a rash does not improve with the use of over-the-counter treatments, see a doctor immediately.
A good way to prevent an allergic reaction to the sun is to wear a sunscreen with a high SPF that blocks both UVA and UVB rays. Also, wear clothing that covers most of your body, such as long sleeves, long pants, sunglasses, and a wide-brimmed hat; the darker the clothing, the better it will protect against the sun's rays. Another good idea is to add UV proctectant to the wash when doing laundry; such a treatment will help your clothing to absorb more sunlight away from your skin.