Polymorphous light eruption (PMLE) is a common skin rash generally caused by exposure to the sun’s ultraviolet (UV) light.
Polymorphous light eruption (PMLE) is a common skin rash that develops after exposure to ultraviolet (UV) light.
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“Polymorphous” means it looks different in different people. “Eruption” refers to the sudden onset of the rash, usually within 30 minutes of UV light exposure. This rash is also known as PMLE, sun allergy or sun poisoning.
Polymorphous light eruption is the most common skin disease resulting from UV light exposure. It may affect up to 15% of people worldwide.
Experts don’t know exactly what causes this rash. It’s possible that UV radiation alters a compound in your skin and your immune system reacts to the new compound.
Both ultraviolet and occasionally visible light cause PMLE. Ultraviolet light has two types: UVA and UVB. UVB can damage your skin, but UVA penetrates deeper into your skin’s layers. UVA causes up to 9 in 10 cases of polymorphous light eruption.
The rash can appear following sun exposure or from other sources such as tanning beds.
PMLE often occurs in the spring when sunny weather returns.
PMLE affects all ages, sexes, races and ethnicities. It’s most common among:
Polymorphous light eruption typically presents as an itchy rash on sun-exposed areas of your body. The rash may consist of small red bumps, larger red patches or even blisters. Skin lesions typically appear within hours of sun exposure, but they sometimes occur days later.
In rare cases, PMLE causes symptoms such as:
In general, symptoms of PMLE last for two to three days. Repeated UV light exposure while the rash is present may cause it to last longer.
PMLE can appear on any part of your body exposed to UV light, although it rarely appears on your face. The rash most commonly appears on your:
Juvenile spring eruption is a type of PMLE that tends to affect the ears of children (mostly boys).
Polymorphous light eruption is typically diagnosed with a thorough health history and skin examination. A skin biopsy, or tissue sample, may be obtained to confirm the diagnosis.
Your healthcare provider may recommend a blood test to rule out other medical conditions, like lupus erythematosus, an autoimmune disease that can also cause a rash following sun exposure.
PMLE typically resolves on its own without treatment.
People living with PMLE should avoid exposure to sunlight, especially between 11 a.m. and 3 p.m., when UV rays are strongest. Using high SPF, broad-spectrum sunscreen, and wearing protective clothing helps minimize UV light exposure.
Some people benefit from phototherapy as a way to “harden” their skin. Repeated, controlled exposure to natural or artificial UV light helps desensitize skin and prevents future rashes.
PMLE starts to fade in a couple of days and goes away without treatment in a few weeks. The rash doesn’t cause scars. However, continual sun or UV exposure can make the rash worse. If you’re going someplace sunny on vacation, your healthcare provider may prescribe an oral corticosteroid like prednisone to reduce your chances of getting a rash.
Some people are able to build a tolerance to UV light by gradually spending time outdoors or using phototherapy. Your provider may refer to this as “hardening the skin.” You should only attempt this type of desensitization while under your provider’s care.
For severe rashes, your provider may prescribe:
This is a recurrent condition that may last for years. But the severity often improves with time.
Call a healthcare provider if you develop an unexplained skin rash or changes to your skin.
If you develop a rash shortly after exposure to sunlight or artificial UV light, ask a healthcare provider if you could have polymorphous light eruption (PMLE).
PMLE is a benign (noncancerous) condition. While the rash doesn’t increase your risk of skin cancer, exposure to UV light does. The sun-protective measures you take to prevent polymorphous light eruption also lower your risk of skin cancer.
A note from Cleveland Clinic
Polymorphous light eruption (PMLE) is a common skin rash that develops in people who are sensitive to ultraviolet (UV) light. This condition causes a red, itchy rash to form soon after you’ve been in the sun or exposed to artificial UV rays. The rash may first appear in the spring and diminish as the spring and summer months progress. Your healthcare provider can suggest ways to protect your skin from UV light and prevent PMLE.
Last reviewed by a Cleveland Clinic medical professional on 02/20/2023.
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