What should you know about sun allergy rash on legs?

When legs are uncovered, ultraviolet exposure can trigger polymorphic light eruption, which may appear as itchy bumps, red patches, or small blisters. Clothing patterns, sunscreen, plants, and medicines can create other explanations. A rash limited to the lower legs can also be affected by friction, swelling, or contact with a product, so location alone does not identify the cause. Compare the rash with covered areas and note whether it follows a sock, hem, or footwear line. Learn more about [Sun Sensitivity](/symptoms/sun-sensitivity/).

Cover the legs with lightweight close-weave clothing and use shade while the skin settles. Wash gently with lukewarm water, apply a fragrance-free moisturiser, and avoid scratching or shaving over inflamed skin. Use sunscreen on exposed areas when leaving home, following the product directions. Do not apply several new creams at once, because that can make the trigger harder to identify. A clinician may recommend [Topical Corticosteroids](/treatments/medical-dermatology/topical-corticosteroids/) for a defined flare. Recurrent episodes may prompt discussion of [Narrowband UVB Phototherapy](/treatments/medical-dermatology/narrowband-uvb-phototherapy/).

Seek assessment if the rash lasts, spreads beyond sun-exposed areas, swells one leg, becomes painful, or develops blisters, pus, or marked warmth. Urgent help is needed for breathing difficulty, facial swelling, faintness, severe pain, or rapidly worsening skin changes. Mention any new medicine, supplement, detergent, sunscreen, or outdoor exposure.

Ask whether the distribution matches sun sensitivity, whether a product or medicine could be contributing, and how to protect the legs during outdoor activity. Ask how to use any prescribed cream and what changes should prompt a review.