Polymorphic light eruption (PMLE) is a common skin reaction triggered by sunlight, usually ultraviolet A (UVA) and sometimes ultraviolet B (UVB) radiation. It often appears in spring or early summer after skin that has had little recent sun exposure is exposed again. PMLE is not the same as eczema and is not contagious.
Symptoms
The rash usually develops within hours to a few days after sun exposure. It commonly affects the chest, arms or lower legs and may cause:
- itchy red or pink bumps
- raised patches or small blisters
- burning or irritation
- swelling in the affected area
The appearance can vary from person to person, but an individual’s outbreaks often look similar each time. The face may be less affected in people who receive regular facial sun exposure.
What causes PMLE?
The exact mechanism is not fully understood. UV radiation appears to trigger an abnormal immune response in susceptible skin. PMLE is more common in women and often begins in adolescence or young adulthood, although anyone can develop it.
Diagnosis
A healthcare professional can often diagnose PMLE from the appearance and timing of the rash and its relationship to sun exposure. Other conditions, including medication-related photosensitivity, lupus and other light-sensitive skin disorders, can cause similar symptoms. Blood tests, phototesting or a skin biopsy may occasionally be needed when the diagnosis is uncertain.
Treatment
Mild outbreaks often improve after avoiding further sun exposure. Cool compresses and fragrance-free moisturizers may soothe irritated skin. A clinician may recommend a topical corticosteroid for an active rash. More persistent or severe cases may require specialist treatment.
Some people with recurrent PMLE undergo medically supervised phototherapy before sunny seasons to gradually increase the skin’s tolerance. Deliberately increasing unprotected sun exposure on your own is not recommended because UV radiation damages skin and increases skin cancer risk.
Prevention
- Use a broad-spectrum, water-resistant sunscreen with SPF 30 or higher.
- Apply sunscreen generously and reapply according to the product directions.
- Wear protective clothing, a broad-brimmed hat and UV-protective sunglasses.
- Seek shade and limit direct sun exposure when UV levels are high.
- Avoid tanning beds and sunlamps.
When to get medical care
Arrange a medical assessment if a sun-related rash is severe, recurrent, widespread, does not improve as expected, or occurs after starting a new medication. Seek prompt care if the rash is accompanied by significant fever, severe weakness, facial swelling, breathing difficulty or other serious symptoms.
Sources and further reading
Last reviewed: 28 September 2026.
This information is general and does not replace individual medical assessment or treatment.