What to know about a rash after sun exposure

The term often refers to polymorphic light eruption, also called PMLE. It is a skin reaction to sunlight rather than an allergy to the sun itself.

PMLE may appear as small raised bumps, red patches or tiny blisters on areas that received sun, often the chest, arms or lower legs. Itching or burning can accompany the rash. The face may be less affected in people whose facial skin receives regular daylight exposure.

The eruption can begin within hours or over the next few days. It often settles without scarring after further exposure stops. Other problems, including medication-related light sensitivity, contact reactions and lupus-related rashes, can resemble it, so recurring, severe or unusual episodes merit assessment.

Move out of direct sun, cover the affected skin and use a cool compress. A plain, fragrance-free moisturiser may soothe dryness. Avoid scratching and pause any new fragranced product used on the area until the cause is clearer.

For future outings, combine shade, tightly woven clothing, a broad-brimmed hat and broad-spectrum sunscreen. Reapply sunscreen according to its label, especially after swimming or heavy sweating. A clinician may recommend a topical corticosteroid for inflammation; repeated seasonal flares may prompt a discussion about supervised narrowband UVB phototherapy before periods of stronger sun.

Arrange a medical review if this is the first significant episode, the rash keeps returning, covers a large area, is painful, leaves marks, or continues despite avoiding sunlight. Bring a list of medicines and supplements because some can increase sensitivity to light.

Seek urgent help for trouble breathing, swelling of the lips or tongue, faintness, widespread blistering, skin peeling, eye involvement, fever or a rapidly worsening rash. These features are not typical of uncomplicated PMLE and need prompt assessment.

Ask whether the timing and distribution fit PMLE, whether a medicine or skin product could be contributing, and which sunscreen texture suits your skin. If episodes are frequent, ask how to use prescribed topical treatment safely and whether preventive phototherapy is appropriate for you. Photographs taken when the rash is fresh can help if it fades before the appointment.