Sun allergy: The 4 Most Common Types (Photosensitivity) – Part 1
March 1, 2012
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If you’ve ever had a sun rash, chances are you’ve suffered from photodermatitis. Learn more about the most common types of sun allergies and their specific symptoms.

What is a sun allergy?

A sun allergy (also called sun poisoning, sun rash and photodermatitis) is a reaction of the immune system to sunlight, most often characterized as an itchy skin rash. Common rash locations include the “V” of the neck, the back of the hands and the arms. In rare cases, the skin reaction may be more severe, producing hives that may even spread to skin in clothed areas.

A sun allergy is not sunburn but might feel like it. Sun allergies are believed to be induced by changes that occur to sun-exposed skin, but real causes are still unknown. Like other autoimmune conditions, the body activates its immune defenses against sun-altered skin. This produces an allergic reaction that takes the form of a skin rash or tiny blisters. In rare cases, other forms of skin eruptions can form as well. While we do not know exactly why some people develop sun allergies, there is evidence that some forms are inherited.

The 4 most common types of sun allergies are:    

  1. Polymorphous light eruption (PMLE), also called Polymorphic Light Eruption (PLE).
  2. Actinic prurigo (hereditary PMLE)
  3. Photoallergic eruption
  4. Solar urticaria

Polymorphous light eruption (PMLE).
PMLE is the most common sun allergy, affecting 10% of North Americans. Main symptoms include itchy or burning rash typically occurring within the first two hours after sun exposure. The rash usually appears on sun-exposed portions of the neck, upper chest, arms and lower legs, and may be accompanied by one to two hours of chills, headache and nausea.

Through repeated sun exposure, the person may become less sensitive to sunlight and the PMLE rash may disappear completely or gradually become less severe. Although the effects of this desensitization process, also called “hardening,” usually lasts through the end of summer, the PMLE rash often returns at full intensity the following spring. A PMLE rash usually disappears within two to three days if further sun exposure is avoided.

Learn more about Polymorphous Light Eruption (PMLE) symptoms and treatments here. (LINK)

Actinic prurigo (hereditary PMLE). This inherited form of PMLE occurs in people of Native American background. Symptoms are usually more severe than classic PMLE and are concentrated on the face, especially around the lips. Several generations of the same family may suffer from this type of allergy.

Photoallergic eruption. This sun allergy is triggered by the effect of sunlight on a chemical that has been applied to the skin (more often an ingredient in sunscreen, fragrances and cosmetics) or ingested such as prescription medication. This usually causes an itchy red rash or tiny blisters. In some cases, eruption spreads to skin covered by clothing.

Common prescription medication that can cause a photoallergic eruption include antibiotics, diuretics for high blood pressure and heart failure, and certain oral contraceptives. Some cases of photoallergic reaction are linked to over-the-counter drugs like ibuprofen (Advil, Motrin and others) and naproxen sodium (Aleve, Naprosyn and others). In most cases, skin symptoms disappear after the offending chemical is identified and no longer used.

Solar urticaria. This form of sun allergy is a rare condition. It produces hives (large, itchy, red bumps) on sun-exposed skin. Solar urticaria most often affects young women. Hives usually appear on uncovered skin within minutes of exposure to sunlight. Symptoms typically fade within 30 minutes to 2 hours. However, they usually come back when skin is exposed to sun again.

Diagnosis

If you have mild symptoms of PMLE, you may be able to diagnose the problem yourself.  Rash occurs only on sun-exposed skin during early spring (or a winter vacation in the Caribbean, for example) then gradually becomes less severe (or disappear) within the following few days or weeks.

If you have more severe sun-related symptoms – especially hives, blisters or small areas of bleeding under the skin, consult a doctor for a proper diagnosis. In most cases, your doctor can confirm that you have PMLE or actinic prurigo based on your symptoms, story and family history (in case of actinic prurigo).

If you have symptoms of a photoallergic eruption, your doctor will begin by reviewing your current medication as well as any skin lotions, sunscreens or colognes you use. The doctor may suggest that you temporarily switch to an alternate medication or eliminate certain skincare products. If necessary, a dermatologist may do photopatch testing, a diagnostic procedure that exposes a small area of your skin to a combination of both ultraviolet light and a small amount of test chemical, usually a medication or ingredient in a skincare product.

If you have symptoms of solar urticaria, your doctor may confirm the diagnosis by using photo-testing alone to reproduce your hives.

If you think you suffer from one of these conditions, learn more about sun allergy prevention, treatments and prognosis.

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