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Polymorphic light eruption

Polymorphic light eruption is a common rash caused by your skin being sensitive to sunlight.

The main symptom of polymorphic light eruption is an itchy or burning rash that can appear after several hours outside on a sunny day.

Polymorphic light eruption usually goes away on its own if there's no further sun damage. A steroid cream or ointment can help settle the rash.

Read more on the NHS website.

The main symptom of polymorphic light eruption is an itchy or burning rash that can appear after several hours outside on a sunny day.

Symptoms of polymorphic light eruption

An itchy or burning rash appears within hours, or up to 2 to 3 days after exposure to sunlight.

It lasts for up to 2 weeks, healing without scarring.

The rash usually appears on the parts of the skin exposed to sunlight, typically the head, neck, chest and arms.

The face is not always affected.

The rash

A rash composed of crops of small red raised spots.

The rash can take many different forms (polymorphic):

Polymorphic light eruption can be easily mistaken for prickly heat.

Prickly heat is caused by warm weather or overheating, rather than sunlight or UV light.

The skin in prickly heat does not "harden" or desensitise, as it can do in polymorphic light eruption.

Polymorphic light eruption is thought to affect about 10 to 15% of the UK population.

Read more on the NHS website.

Polymorphic light eruption usually goes away on its own if there's no further sun damage. A steroid cream or ointment can help settle the rash.

Medical treatments

There's no cure for polymorphic light eruption, but using sunscreens and careful avoidance of the sun will help you manage the rash.

Avoid the sun, particularly between 11am and 3pm when the sun's rays are at their strongest, and wear protective clothing when outdoors (unless you're hardening your skin).

Introduce your skin to sunlight gradually in the spring.

Sunscreen

You may be prescribed sunscreens to help prevent the rash developing.

Use a sunscreen that is SPF 30 or above with a good UVA rating. Apply sunscreen thickly and evenly reapplying often.

Steroid creams and ointments 

Your GP can prescribe corticosteroid (steroid) cream or ointment that's only applied when the rash appears.

You should apply it sparingly, as often as your GP advises, and never when there's no rash.

Desensitisation or UV treatment

It's sometimes possible to increase the resistance of your skin to the sun.

This involves visiting a hospital dermatology department 3 times a week for 4 to 6 weeks in the spring.

Your skin is gradually exposed to a little more UV light every visit to try to build up your skin's resistance.

The effects of desensitisation are lost in the winter, so you'll have to build up your resistance again in the spring.

Hardening or toughening

You may be able to increase the resistance of your skin at home.

This is known as "hardening" and involves going outside for short periods in the spring to build up your resistance.

You might find the time is as short as a few minutes at first, but you may be able to gradually build up to longer times.

You'll have to be careful not to overdo it but, as you begin to understand more about how much light triggers your rash, you'll be able to judge how long to stay out.

Like desensitisation, the effects of hardening are lost in the winter, so you'll have to build up your resistance again in the spring.

Vitamin D

People with polymorphic light eruption are at greater risk of vitamin D deficiency, as a certain amount of sun exposure is needed to make your own vitamin D.

Your GP will advise whether you need treatment with vitamin D supplements.

Read more on the NHS website.