Polymorphous light eruption
Polymorphic light eruption; Photodermatosis; PMLE; Benign summer light eruptionPolymorphous light eruption (PMLE) is a common skin reaction in people who are sensitive to sunlight (ultraviolet light).
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Causes
The exact cause of PMLE is unknown. However, it may be genetic. Health care providers think it is a type of delayed allergic reaction. It is common among young women who live in moderate (temperate) climates.
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Symptoms
Polymorphous means taking on different forms, and eruption means rash. As the name suggests, symptoms of PMLE are rash-like and are different in different people.
PMLE most often occurs in spring and early summer on areas of the body exposed to the sun.
Symptoms usually appear within 1 to 4 days after exposure to sunlight. They include any of the following:
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Exams and Tests
Your provider will examine your skin. Usually, your provider can diagnose PMLE based on your description of the symptoms.
Tests that may be done include:
- Phototesting, during which your skin is exposed to special ultraviolet light to check if your skin develops a rash
- Removing a small amount of skin for examination skin biopsy to rule out other diseases
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Treatment
Steroid creams or ointments containing vitamin D may be prescribed by your provider. They are used 2 or 3 times a day at the start of the eruption. Steroid or other types of pills may be used for more severe cases.
Phototherapy may also be prescribed. Phototherapy is a medical treatment in which your skin is carefully exposed to ultraviolet light. This may help your skin become used to (sensitized to) the sun.
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Outlook (Prognosis)
Many people become less sensitive to sunlight over time.
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When to Contact a Medical Professional
Call for an appointment with your provider if PMLE symptoms do not respond to treatments.
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Prevention
Protecting your skin from the sun can help prevent PMLE symptoms:
- Avoid sun exposure during hours of peak sun ray intensity.
- Use sunscreen. Sun protection with broad spectrum sunblock that works against UVA rays is important.
- Apply generous amounts of sunscreen with a sun protection factor (SPF) of at least 30. Pay special attention to your face, nose, ears, and shoulders.
- Apply sunscreen 30 minutes before sun exposure so that it has time to penetrate the skin. Re-apply after swimming and every 2 hours while you are outdoors.
- Wear a sun hat.
- Wear sunglasses with UV protection.
- Use a lip balm with sunscreen.
References
Ling TC. Polymorphic light eruption. In: Lebwohl MG, Heymann WR, Coulson IH, Murrell DF, eds. Treatment of Skin Disease: Comprehensive Therapeutic Strategies. 6th ed. Philadelphia, PA: Elsevier; 2022:chap 196.
Patterson JW. Reactions to physical agents. In: Patterson JW, ed. Weedon's Skin Pathology. 5th ed. Philadelphia, PA: Elsevier Limited; 2021:chap 22.