A sun allergy is a reaction of the immune system, caused by sensitivity to sunlight. Also known as photosensitivity, this condition develops when the sun-exposed skin reacts abnormally to sunlight. Scientist are still not able to understand the exact cause of this condition, though some studies indicate that it is inherited. Apart from this, it may also be triggered due to certain chemicals, medications, or medical conditions. There are mainly four types of sun allergies; namely polymorphous light eruption, actinic purigo, photoallergic eruptions, and solar urticaria. The symptoms and treatments depend on the type of allergy. The types, their symptoms and treatment options are explained here. Symptoms and Treatment Polymorphous Light Eruption (PMLE) The symptoms of PMLE are, an itchy or burning skin rash and red plaques or small fluid-filled blisters that may bleed on rupture. It occurs within a couple of hours after sun-exposure and at times maybe accompanied by chills, headache, or nausea. It usually develops on exposed portions of the neck, upper chest, arms, and lower legs. They tend to disappear on their own in a couple of days, but for some people it keeps re-occurring every spring and summer. However, this causes a decrease in the skin's sensitivity to sunlight. A mild reaction may be treated using a cold compress or spaying the skin with cold water in frequent intervals. A more severe or hardened allergy is treated through medications such as an oral antihistamine, like diphenhydramine or chlorpheniramine, or any anti-rash skin cream containing cortisone. In extreme cases, doctors usually prescribe photo therapy treatment, where the skin is gradually exposed to ultraviolet light (UV), in small and frequent doses to build skin resistance to the rays. Sometimes, a combination of psoralen and ultraviolet light, antimalarial drugs or beta-carotene tablets may also be used to treat this condition. Actinic Prurigo This form is an inherited form of PMLE. As its nature is inheritable, it begins early in life during childhood or adolescence. The symptoms are same as that of PMLE, but the rash occurs more on the face, especially on the lips. It re-occurs in spring and summer, while in tropical climates it persists round the year. It is treated using medications that include corticosteroids, thalidomide, antimalarial drugs, beta-carotene, and UV, depending on the severity of the allergy. Photoallergic Eruption At times when the skin is exposed to sun, it reacts to the chemicals present on the skin, such as that in sunscreen, fragrances, cosmetics, or ointments and even to some prescribed drugs. This reaction produces tiny red rashes or fluid-filled blisters on the skin. It may also spread to other parts of the skin that are covered. Most of the time, these symptoms develop after 2 to 3 days of sun exposure. The most common treatment option for this condition other than corticosteroid cream, is to find and eliminate the allergy causing product. Solar Urticaria This rare form of allergy is considered to be the only true form of sun allergy. It causes hives on the affected parts of the skin. It exhibits symptoms within minutes of exposure to sunlight, and if the hives are formed individually, they fade away within a couple of hours. Its treatment depends upon the severity of the condition. For mild allergies, oral antihistamine or an anti-itch cream, containing cortisone is prescribed. For severe symptoms, a combination of psoralen and ultraviolet light, antimalarial drugs or beta-carotene tablets may be used. Some over-the-counter medications like vitamin E, aloe vera lotion, and quercetin (flavonoids) may also be used. Besides these, preventive measures like using a good quality and high SPF sunscreen, and sun protection gear, may be used regularly. Also, since exposure to sunlight cannot be avoided, a few simple preventive steps may be taken to lessen the agony of dealing with sunburns and rashes.