Polymorphic light eruption is a rash that occurs in response to sunlight after a period of time in which the skin has been exposed to the sun. Sometimes as little as 15 minutes' exposure to the sun can induce the condition. As it is caused by ultraviolet light it can even occur after sun exposure through a window.
It is a fairly common condition, affecting 15% of people in the UK. It's more common with women and those with fairer skin from the age of 20-40 years. People who can quite easily, even those with dark skin, may still get polymorphic light eruption.
The precise nature of the cause of polymorphic light eruption is unknown, but it is likely to be caused by an allergic reaction to a substance in the skin that is chemically altered by UV radiation, and therefore appears foreign to the body.
An itchy rash is caused within hours of sun exposure, causing a onset of raised pink and red spots, sometimes even blisters. This can occur on any part of the body that has been exposed to the sun, most commonly on the arms, chest or lower legs. Occasionally a flu-like illness develops too.
Sometimes your skin will build tolerence to the sun as sun exposure increases, however that is not always the case.
Protecting yourself from the sun with protective clothing and a high factor sunscreen (note these might not filter out all sunlight).
Gradually exposing yourself to the sunlight may acclimatise the skin and prevent the rash from occurring.
For an acute condition
Topical steroids may be prescribed by your dermatologist.
Antihistamines may help stop the itching, (note can cause photosensitivity).
For severe conditions
Prophylactic light therapy could be suggested by your Dermatologist, (before sun exposure i.e spring time). It could help "photoharden" your skin by aiming to induce sunlight tolerence using controlled exposure.
Beta-carotene (vitamin) and hydroxychloroquine (antimalarial drug) can improve tolerence to the sun.
Sometimes long term polymorphic light eruption often improves over time and may reslove in some patients