Sun Allergy: Definition, Causes, and Treatment

An allergic reaction or increased sensitivity to the sun consists of a series of skin problems or dermatosis with the common feature of the appearance of allergic symptoms such as a skin rash following exposure to the sun.

Photodermatosis is very common, it can affect up to 10% of the population and the most common form, accounting for over 90% of cases, is polymorphic light eruption.

What is photodermatosis?

It is a skin disorder caused principally by exposure to ultraviolet radiation. It happens when the skin has an abnormal reaction to sunlight. This is because sunlight damages the surface of the skin by creating free radicals. Skin with this condition is more sensitive to the appearance of free radicals and to defend itself, skin immunity is activated in an exaggerated fashion. This process causes an allergic reaction related to type IV immunoglobulins. So, when it is activated abnormally, the regular clinical presentation is encountered with the appearance of skin lesions.

What are the symptoms of sun allergy?

There are usually various symptoms. The most common is that it starts with a mild rash or outbreak of pustules. However, skin erythema or vesicles can also be present, although the most characteristic symptom is intense irritation with associated itching. It is described as being recurrent and occurs in outbreaks. Symptoms can appear immediately after exposure or some days later.

It most commonly affects young women and pale-skinned people. The season for the onset of the appearance of symptoms is usually spring, running through to autumn.The parts of the body most commonly affected are the outside of the arms, the chest and, less frequently, the face.

Can sun allergy be prevented?

Prevention is fundamental to ensuring that photodermatosis does not become chronic and symptoms get worse.

  • Always use sunscreen when you are going to be exposed to the sun. This will not only protect your skin but can alleviate symptoms.
  • Limit exposure to the sun during the hottest hours to avoid excessive absorption of solar radiation by your skin.
  • Cover up in light clothing to prevent contact and allergic sensitivity.
  • Take cycles of prophylactic phototherapy or sun desensitisation processes at the start of spring. This involves gradual and progressive exposure to UV radiation. It will boost tolerance to exposure and reduce symptoms. Photodermatosis can improve and even completely disappear.​

How is photodermatosis treated?

Treatment is symptomatic, i.e. aimed at relieving symptoms. Recurrent outbreaks of photodermatosis usually focus on itching. Use calming and moisturising lotions which can reduce symptoms and irritation. Because it is an allergic reaction, you may need to apply corticosteroids to the skin, or take oral treatments in severe cases.

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