What causes rash with fever?

Fever suggests that the immune system is responding to something beyond a simple local irritation, although the cause cannot be diagnosed from a description alone. Cellulitis often affects one area with spreading redness, warmth, swelling or tenderness. Chickenpox can produce an itchy eruption with spots at different stages. A medicine-related eruption may appear after starting or changing a drug. A severe reaction such as Stevens-Johnson syndrome can involve painful skin, blisters, peeling or sores on the mouth, eyes or genitals.

Record when the fever and rash began, where the rash started, how it has spread, and every medicine or supplement taken recently. Avoid starting leftover antibiotics or stopping a prescribed medicine without medical advice; contact the prescriber promptly if a new medicine may be involved. Drink fluids if you can, rest, and use a thermometer to monitor the fever while arranging clinical advice.

Seek urgent care for a rapidly spreading rash, severe pain, purple or bruise-like spots, blisters, peeling skin, facial swelling, breathing difficulty, confusion, faintness or sores in the mouth or eyes. A fever with a very unwell appearance also needs prompt assessment. Children, older adults and people with weakened immunity should be assessed early.

Ask what the rash pattern suggests, whether testing is needed, and whether any recent medicine could be responsible. Tell the clinician about exposures, sick contacts, vaccination history, travel, allergies and symptoms such as cough, sore throat, joint pain or stomach upset.