Why does drug rash cause sun sensitivity?

Some medicines absorb ultraviolet energy and transfer that energy to nearby skin cells, while some immune reactions make already inflamed skin easier to irritate. Exposed areas may become red, warm, itchy, sore, or develop a rash after ordinary daylight. The reaction can be stronger on the face, neck, arms, and backs of the hands. A drug rash can also remain sensitive after the medicine is changed, so the timing should be discussed with a clinician.

Limit direct sun while the rash is active, use closely woven clothing and a wide-brimmed hat, and seek shade when outdoors. Ask a pharmacist or clinician which sunscreen is suitable for your skin and medicines. Do not stop a prescribed treatment or substitute another one without advice. Keep a record of sun exposure, the medicine schedule, and whether the rash burns, itches, or spreads.

Arrange prompt medical review for a new rash that worsens in sunlight, especially with fever or marked tenderness. Seek emergency care for breathing problems, facial swelling, blistering, peeling, skin pain, faintness, or sores involving the mouth or eyes. These features can signal a more extensive reaction than ordinary photosensitivity.

Ask whether the medicine is known to increase light sensitivity, which parts of the ultraviolet spectrum matter, and how long precautions may be needed. Ask what to do if the rash returns after a brief exposure and whether another medicine is appropriate.