It's rare, but it IS possible to have what appears to be an allergic response to sunlight, but it's not a true allergy. In true allergies, the body is reacting to a foreign substance. In sun allergies, the body is reacting to the natural changes in the skin brought about by exposure to the sun. We don't know why, but in some sensitive people the immune system erroneously recognizes a component of sun-altered skin as a foreign object and initiates its defenses against it. This manifests as a rash, tiny blisters or, in its extreme form, a type of skin eruption.
There are a lot of unknowns about so-called sun allergies. It is unknown why the body reacts the way it does. It is unknown why it happens to some people, but not the vast majority. There is evidence that sun allergies may be inherited.
There are 4 common types of sun allergy:
PMLE, or polymorphous light eruption, is the most common. This type of sun allergy occurs in 10 to 15% of the population. It affects all races, but women seem to be more prone to it than are men. Symptoms usually begin in early adulthood.
It appears as an itchy rash within the first two hours of exposure to the sun. It can be anywhere the sun has hit - most often the neck, upper chest, arms and lower legs. The rash will last two to three days, as long as further exposure to the sun is avoided. There may be accompanying chills, headache and nausea. In rare cases PMLE may turn into red flat, raised areas and small blisters or tiny areas of bleeding under the skin may be experienced. It's at its worst in the beginning of the summer, but prolonged exposure gradually reduces its intensity or may even cause it to disappear later in the season, only to repeat this entire cycle the next year.
Treat mild symptoms with cool compresses. Mist your skin with cool water. An over-the-counter antihistamine will help the itching. More severe symptoms may require your doctor to prescribe a stronger antihistamine or corticosteroid cream. Phototherapy may be used to harden and deaden the reaction with the use of ultraviolet light in your doctor's office.
The second type, actinic prurigo, is commonly called "hereditary PMLE", as it is very similar to PMLE above, except the symptoms are usually concentrated on the face, especially around the lips. It also differs from PMLE in that it only occurs in people of American Indian descent. It appears earlier than PMLE -- in childhood or teenage years and its symptoms may be more intense. Treatment would be similar to that of severe PMLE.
Photoallergic eruptions are triggered by sunlight's effect on a chemical that has been applied to the skin, such as a sunscreen, cosmetic, fragrance or ointment; or an ingested drug. Some drugs that are known to have caused photoallergic eruptions are antibiotics, psychiatric drugs and diuretics for high blood pressure, oral contraceptives and even some over-the-counter pain relievers. The symptoms are similar to PMLE but they occur later. The rash or tiny blisters may not show up for a couple days after the sun exposure. Its duration is unpredictable. It can also spread to areas of skin that were covered and not directly exposed to the sun. All these things sometimes make it difficult to identify the culprit product.
The first treatment goal is to identify and eliminate the medicine or skin care product causing the reaction. As soon as that is done the patient will probably never have another allergic reaction in the sun. In the meantime corticosteroid creams can be applied to relieve the symptoms.
Solar urticaria produces large, itchy hives on sun-exposed skin. The hives appear within minutes of sun exposure. They will disappear in 30 minutes to two hours. This is the rarest of the four sun allergies and most often affects young women. Treatment is the same as with PMLE.
If you have sun allergies the outlook is usually very good. Today the wealth of sunscreens available makes the sun avoidable while outdoors! Just watch and strictly limit the amount of time you spend in the sun. Be consistent in sunscreen use and wear protective clothing, even if it's a cloudy day. Most people improve dramatically within a few years of diagnosis.
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