Polymorphous light eruption is a rash caused by sun exposure in people who are sensitive to sunlight. Polymorphous means that the rash can have many forms, such as tiny bumps, raised areas or blisters. The condition also is called sun allergy, sun poisoning and polymorphic light eruption.

Polymorphous light eruption is a rash that affects parts of the body that are exposed to more sunlight as daylight hours get longer, such as the front of the neck and chest. Polymorphous means that the rash can have many forms, such as tiny bumps, raised areas or blisters.

The reaction usually happens during spring and early summer when exposure to sunlight increases. It's less likely to be repeated as the summer progresses. But the rash often happens again each year after the first time. If you're going to develop this sensitivity, the first instance will likely be in your teens or 20s.

Polymorphous light eruption usually goes away on its own without scarring within 10 days. People with severe or persistent rashes may need medicine.

Symptoms of the rash in polymorphous light eruption may include:

• Dense clusters of small bumps and blisters.

• Inflamed, raised rough patches.

• Itching or burning.

The rash that results from polymorphous light eruption can look different from person to person but typically includes inflammation, itching and small bumps that may be densely packed together.

People may rarely have other symptoms such as fever and chills.

In polymorphous light eruption, eruption refers to the rash, which usually appears 30 minutes to several hours after sun exposure. The rash usually appears on areas of the body that are covered during winter but exposed in summer such as the upper chest, front of the neck and arms.

See your healthcare professional if you have any rash with no obvious cause, such as a known allergy or recent contact with poison ivy.

Polymorphous light eruption rashes look like rashes caused by other diseases, some of which are serious. So, it's important to get a prompt diagnosis and treatment.

Seek immediate medical care if your rash:

• Is widespread.

• Is painful.

• Comes with a fever.