Rash from a sulfa drug: what to know

Sulfa medicines include some antibiotics and other prescription drugs. A reaction can cause red patches, raised spots, itching, or hives. It may begin soon after a dose or appear after several days. A rash can have other causes, including a viral illness or a separate skin condition, so its appearance alone cannot identify the trigger. A drug rash is one possible explanation; read about Drug Rash when comparing patterns.

Contact the prescriber or a pharmacist promptly and give the medicine name, dose, start date, and time the rash began. Do not restart the medicine or use a related product unless a clinician tells you to. Take clear photographs and keep a list of every medicine, supplement, and topical product used recently. A cool compress and loose clothing may reduce irritation. Do not apply a new cream that could further confuse the picture.

Get emergency help for trouble breathing, swelling of the lips or tongue, faintness, or widespread hives. Seek urgent medical assessment for skin pain, blisters, peeling, sores in the mouth or eyes, fever, or rapidly spreading redness. These features can signal a serious medicine reaction and need prompt evaluation.

Ask whether the medicine should be recorded as a suspected allergy, which alternatives are appropriate, and whether you need an examination or treatment. Ask what symptoms should make you seek emergency care if the rash changes.