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, also known as polymorphic light eruption, is a rash caused by sun exposure in people who have developed sensitivity to sunlight. The rash usually appears as red, tiny bumps or slightly raised patches of skin.
Polymorphous light eruption occurs most often during spring and early summer when a person's exposure to sunlight increases. Repeat episodes are less likely as the summer progresses. But the rash often recurs each year after the first incident.
Polymorphous light eruption usually goes away on its own without scarring within 10 days. People with severe or persistent rashes may need treatment with medication.
The term "eruption" refers to the rash, which usually appears 30 minutes to several hours after exposure to sunlight. The rash typically appears on areas of the body that tend to be covered during winter but exposed in summer: the upper chest, front of the neck and arms.
Characteristics of the rash may include:
Rarely people may have other signs or symptoms, such as fever, chills, headache or nausea. These conditions may be the result of an associated sunburn rather than polymorphous light eruption.
When to see a doctor
See your doctor 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 appropriate treatment.
Seek immediate medical care if your rash is:
The exact cause of polymorphous light eruption isn't well-understood. The rash appears in people who have developed sensitivity to components of sunlight, and in particular ultraviolet (UV) radiation from the sun or other sources, such as tanning beds or tanning lamps. This sensitivity is called photosensitivity. It results in 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. Although UVB doesn't penetrate glass, UVA does. UVA may even penetrate through most sunscreens. So exposure to sunlight through windows or even sunscreen-protected skin may cause a reaction in some people with photosensitivity.
Sensitivity to sunlight lessens with repeated exposure in polymorphous light eruption. 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 doctor can probably make a diagnosis of polymorphous light eruption based on a physical exam and your answers to questions. He or she may also have you undergo laboratory tests in order to confirm a diagnosis or rule out other conditions. Tests may include:
Your doctor may need to rule out other disorders characterized by light-induced skin reactions. These conditions include:
Treatment of polymorphous light eruption usually isn't necessary because the rash typically goes away on its own within 10 days. If your symptoms are severe, your doctor may prescribe anti-itch medicine (a corticosteroid cream or pill). Treatment is also available to help prevent a rash.
Your doctor may suggest phototherapy to prevent seasonal episodes of polymorphous light eruption in people who have experienced disabling signs and symptoms. Phototherapy exposes your skin to small doses of UVA or UVB light, which helps your skin be less sensitive to light. Basically, it's a controlled version of the increased exposure you would experience over the course of the summer.
One type of light therapy called psoralen plus ultraviolet A (PUVA) combines UVA with a medicine called psoralen, which makes the skin more sensitive to this light. Short-term side effects of this therapy may include nausea, headache and itching.
Self-care measures that may help ease your signs and symptoms include:
To lessen the likelihood of recurring episodes of polymorphous light eruption, take the following precautions:
Use sunscreen. Fifteen to 30 minutes before going outdoors, apply a broad-spectrum sunscreen, one that provides protection from both UVA and UVB light. Use a sunscreen with a sun protection factor (SPF) of at least 30. Apply sunscreen generously, and reapply every two hours — or more often if you're swimming or perspiring. If you're using a spray sunscreen, be sure to cover the entire area completely. Cover up. For protection from the sun, wear tightly woven clothing that covers your arms and legs and a broad-brimmed hat, which provides more protection than does a baseball cap or golf 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 doctor include:
Your doctor 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.
December 24th, 2020