"Sun allergy" - Overview

Too much sun can lead to sunburn and long-term skin damage (such as early signs of aging and skin cancer) – as every beachgoer knows. But some people, even a small amount of sunlight is problematic or even dangerous. For patients with skin diseases caused or made worse by sunlight, the summer holiday season is the worst time of year.

The term "sun allergy" is not a medical term, but is used commonly by patients to describe a series of conditions in which the skin becomes irritated or inflamed following contact with sunlight. These include:

Polymorphous Photodermatosis:
This is the most common sun-related skin problem. Three times as many women are afflicted as men. The appearance of photodermatosis varies from patient to patient (that’s why it’s called "polymorphous"). After contact with sunlight, patients notice redness, blisters, or swelling of the skin in areas exposed to the sun. These itching or burning symptoms appear anywhere from a few hours to two days after contact with sunlight. The symptoms appear most often following the first intensive exposure to sunlight of the year – usually in early summer or at the beginning of a beach holiday. The cause is generally an intolerance to the sun’s UVA rays.  Mild cases abate after a few weeks, even with further contact with sunlight. However, in the following year the symptoms appear again.

"Mallorca Acne" (Acne aestivalis):
Again more prevalent in women than in men; itchy bumps appear on the skin where sunscreen has been applied. It is believed that this is a reaction caused by the combination of oily sunscreen and sweat.

Phototoxic Dermatitis:
Certain substances, when applied to the skin, can make the skin oversensitive to sunlight. Some plant-based substances, such as furocumarine, can cause sunburn-like redness and blisters if the skin is exposed to sunlight. Substances taken internally – including diuretics and tetracycline antibiotics – can also cause a phototoxic skin reaction. 

Photoallergic Dermatitis:
Following external or internal use of certain substances or medications, the skin reacts with allergic eczema when exposed to sunlight. These allergic reactions occur when ultraviolet light from the sun alters certain chemicals, turning them into allergens.  

Light urticaria:
Some patients experience hives (wheals) after contact with the sun. A few minutes after contact with sunlight, redness and itchy hives appear on the skin. This illness is very rare.

Some illnesses are made worse or triggered by contact with sunlight, such as Lupus Erythematodes (and other autoimmune illnesses) or porphyria, a group of metabolic diseases.

All of these illnesses (apart from photoallergic dermatitis) are caused by intolerance reactions, rather than by true allergic reactions.

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