Exanthematous drug eruption: what to know

The rash often consists of small flat or slightly raised spots that begin on the trunk and spread to the limbs. It may itch and can develop days after a new medicine, a dose change or, sometimes, re-exposure to a medicine used before. The timing is helpful but does not prove which product is responsible. Viral illness, contact reactions and other rashes can look similar. A clinician will consider every medicine, supplement and recent illness rather than relying on the appearance alone.

Write down the medicine names, doses, start dates and the time the rash appeared. Contact the prescriber or a pharmacist promptly before making changes to an essential medicine; they can advise whether it should be paused, replaced or continued. Avoid taking leftover treatments without advice. Keep the skin cool, use gentle fragrance-free products and avoid scratching. A clinician may recommend an oral antihistamine or a topical corticosteroid when appropriate.

Get emergency help for trouble breathing, faintness, swelling of the lips or tongue, skin pain, widespread blistering, peeling, sores in the mouth or eyes, or a high fever. Seek same-day assessment if the rash is rapidly spreading or you feel significantly unwell. These features may signal a more serious reaction than a simple exanthematous eruption.

Ask which medicine is most suspicious, whether an alternative is available, how to record the reaction, and which future medicines should be avoided. Ask what symptoms require emergency care and whether follow-up testing is needed.