Learn more about the symptoms and treatments for this sun-induced skin rash that usually appears in spring or summer, and also after using tanning beds.
Polymorphous light eruption is a rash caused by sun exposure in people who have developed sensitivity to sunlight. The rash usually appears as tiny, inflamed bumps or slightly raised patches of skin.
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.
The condition is also known as polymorphic light eruption, sun allergy and sun poisoning.
Polymorphous light eruption usually goes away on its own without scarring within 10 days. People with severe or persistent rashes may need medication.
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.
Symptoms of the rash in polymorphous light eruption may include:
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 health care provider 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 similar to 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:
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.
The exact cause of polymorphous light eruption isn't understood. The rash appears in people who have developed sensitivity to sunlight, especially ultraviolet (UV) radiation from the sun or other sources, such as tanning beds. This is called photosensitivity. It leads to immune system activity that causes a rash.
UV radiation is a wavelength of sunlight in a range too short for the human eye to see. UV light that reaches the earth is divided into two wavelength bands — ultraviolet A (UVA) and ultraviolet B (UVB).
A person with photosensitivity can react to both types of UV radiation. UVB doesn't penetrate glass. UVA does. Exposure to sunlight through windows or even sunscreen-protected skin may cause a reaction in some people with photosensitivity.
With polymorphous light eruption, sensitivity to sunlight lessens with repeated exposure. Features of polymorphous light eruption are somewhat predictable:
Anyone can develop polymorphous light eruption, but several factors are associated with an increased risk of the condition:
Your health care provider can probably make a diagnosis of polymorphous light eruption based on a physical exam and your answers to questions. Your health care provider might have you undergo laboratory tests in order to confirm a diagnosis or rule out other conditions. Tests may include:
Your health care provider might need to rule out other disorders characterized by light-induced skin reactions. These conditions include:
Treatment of polymorphous light eruption usually isn't needed because the rash usually goes away on its own within 10 days. If your symptoms are severe, your health care provider may prescribe anti-itch medicine (a corticosteroid cream or pill).
Your health care provider may suggest phototherapy to prevent seasonal episodes of polymorphous light eruption if you have disabling symptoms. This exposes the skin to small doses of UVA or UVB light that helps your skin be less sensitive to light. It mimics the increased exposure you would experience during a summer.
Self-care measures that may help ease signs and symptoms include:
To lessen the likelihood of recurring episodes of polymorphous light eruption, take the following precautions:
Cover up. For protection from the sun, wear tightly woven clothing that covers your arms and legs. Consider wearing a broad-brimmed hat, which provides more protection than does a cap or visor.
Consider wearing clothing designed to provide sun protection. Look for clothes labeled with an ultraviolet protection factor (UPF) of 40 to 50. Follow care instructions on the label of UV-blocking clothes to maintain their protective feature.
You're likely to start by seeing your primary care doctor. He or she may refer you to a specialist in skin diseases (dermatologist).
Here's some information to help you get ready for your appointment.
For polymorphous light eruption, some basic questions to ask your health care provider include:
Your health care provider will ask you a number of questions about your symptoms and your medical history, such as:
Avoid sun exposure whenever possible. If you can't avoid the sun, use a broad-spectrum sunscreen with an SPF of at least 30 in areas that cannot be protected by clothing. Apply it generously 15 minutes before sun exposure. Reapply it every two hours or more often if you're swimming or sweating. This won't totally protect you from a reaction, as ultraviolet A may penetrate through most sunscreens.