What is polymorphous light eruption?
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.
How common is polymorphous light eruption?
Polymorphous light eruption is fairly common. It is more common in women than men. It particularly affects those who are fair, although it can affect those with dark skin. It usually starts from the ages of 20 to 40, although it sometimes affects children. Please discuss with your doctor for further information.
What are the symptoms of polymorphous light eruption?
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:
- Dense clusters of small bumps and blisters
- Red, raised rough patches
- Itching or burning
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.
There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.
When should I see my 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:
- Accompanied by fever
What causes polymorphous light eruption?
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:
- An episode is most likely to occur after the first one or two exposures to sunlight after a long period of no exposure. This usually means that an episode occurs during the spring or early summer or during a winter vacation in a sunnier location.
- Episodes are less likely to occur as the summer progresses.
- After the first episode of polymorphous light eruption, additional episodes are likely to recur each spring or early summer.
Some people gradually become less sensitive over several years and eventually no longer experience the annual rash.
What increases my risk for polymorphous light eruption?
There are many risk factors for polymorphous light eruption, such as:
- Being female
- Experiencing the first episode during the teenage years or 20s
- Having light skin and living in northern regions
- Having a family history of the condition
Diagnosis & treatment
The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.
How is polymorphous light eruption diagnosed?
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:
- Skin biopsy. Your doctor may remove a sample of rash tissue (biopsy) for examination in a lab.
- Blood tests. A nurse or assistant may draw blood for laboratory tests.
- Your doctor may refer you to a specialist in skin conditions (dermatologist) for phototesting. During the test small areas of your skin are exposed to measured amounts of UVA and UVB light to try to reproduce the problem. If your skin reacts to the UV radiation, you’re considered sensitive to sunlight (photosensitive) and may have polymorphous light eruption or another light-induced disorder.
How is polymorphous light eruption treated?
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.
Lifestyle changes & home remedies
What are some lifestyle changes or home remedies that can help me manage polymorphous light eruption?
The following lifestyles and home remedies might help you cope with polymorphous light eruption:
- Applying anti-itch cream. Try an over-the-counter (nonprescription) anti-itch cream, which may include products containing at least 1 percent hydrocortisone.
- Taking antihistamines. If itching is a problem, oral antihistamines may help.
- Using cold compresses. Apply a towel dampened with cool tap water to the affected skin, or take a cool bath.
- Leaving blisters alone. To speed healing and avoid infection, leave blisters intact. If needed, you can lightly cover blisters with gauze.
- Taking a pain reliever. An over-the-counter pain medication may help reduce redness or pain. These include ibuprofen (Advil, Motrin IB, others), acetaminophen (Tylenol, others) and naproxen sodium (Aleve, others).
- Avoid the sun between 10 a.m. and 2 p.m. Because the sun’s rays are most intense during this time, try to schedule outdoor activities for other times of the day.
- 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
If you have any questions, please consult with your doctor to better understand the best solution for you.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Polymorphous light eruption. https://www.mayoclinic.org/diseases-conditions/polymorphous-light-eruption/symptoms-causes/syc-20355868. Accessed November 30, 2017.
Polymorphic light eruption. https://www.nhs.uk/conditions/polymorphic-light-eruption/. Accessed November 30, 2017.
Review Date: November 30, 2017 | Last Modified: December 1, 2017