What is Sun Allergy?

A sun allergy or photosensitivity, in some people, is an allergic reaction caused due to exposure of skin to sunlight. The term ‘allergy’ denotes a hypersensitive response within the body to certain foreign substances known as allergens. In an allergic response, the immune system is activated causing it to form antibodies that try to destroy or neutralise the foreign antigens (the allergens).

In people with sun allergy, an allergic reaction occurs in response to exposure to sunlight. In a person with sun allergy, his or her body reacts to the natural changes in the skin that occur after exposure to the sun. Their immune system on exposure to sunlight begins to treat the skin as if it were something 'foreign' and tries to defend it. The exact cause and why this disorder happens in certain individuals and not others is not known.

The common symptoms of sun allergy include rash, tiny blisters or, in its extreme form, a type of skin eruption, such as hives or large blisters on the skin (not only on exposed areas, but under clothing too). The symptoms usually begin on areas that are exposed to sun, such as the back of the hands, the outside areas of the arms, lower legs and neck.

The different types of sun allergy include:

• Polymorphic light eruption (PMLE),
• Actinic prurigo,
• Chronic actinic dermatitis (CAD) and
• Solar urticaria.

Polymorphic light eruption (PMLE): This is the second most common cause of medical problems caused due to exposure to sun (the most common reaction of skin to exposure to sun is sunburn). 'PMLE' causes typical red itchy rashes on the skin after its exposure to sun. It may occur in individuals of all races. It most commonly starts during young adulthood and is more common in women than men.

'Actinic Prurigo' or 'hereditary PMLE': This is a type of 'PMLE', which is inherited i.e. you are more likely to experience it if you have a positive family history. It generally occurs in individuals of American-Indian descent and starts during childhood or adolescence.

Photoallergic eruption: It is a common cause of photosensitivity caused due to reaction with a certain chemical that has been applied to the skin or prescription medication, which has been ingested. Any skin product, which is applied to the skin, such as certain lotions, fragrances or sun screens can cause photoallergic eruption. Prescription medications that can cause photoallergic eruption include certain antibiotics, high blood pressure medications and psychiatric medications.

Solar Urticaria: It is a rare type of sun allergy, which can become a long-term problem. It causes chronic hives on exposure to sunlight and typically affects younger women.

The symptoms of an allergic reaction to sun may last for a short duration (a few hours) or a couple of days. If your symptoms are bothersome, consult your doctor to confirm the diagnosis and treatment. If you have sun allergy, the best treatment is prevention of exposure to sun.

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