Fever with an urticarial rash: what to know

Urticaria causes raised, itchy areas that can change shape or move to different parts of the skin. Each mark may fade while another appears. Fever can occur with infections such as a common cold, COVID-19 or chickenpox; it can also reflect another illness rather than the rash itself. A new food, medicine or insect sting may trigger hives. The timing of exposure, the appearance of the rash and other symptoms help a clinician judge the cause.

Take a photograph if the rash changes quickly, and write down new foods, medicines, supplements or products used before it started. Keep the skin cool, avoid scratching and use gentle, fragrance-free products. A pharmacist can advise whether an antihistamine is suitable. Do not stop an essential prescribed medicine without medical advice, but seek prompt guidance if the rash followed a new medicine.

Call emergency services immediately for swelling of the lips, tongue or throat, wheezing, breathing difficulty, repeated vomiting, collapse, or marked dizziness. Seek same-day medical advice for a rapidly spreading rash, painful skin, blisters, mouth or eye sores, a child who appears very unwell, or fever that persists or worsens. Hives with breathing or circulation symptoms can be an emergency even if the rash looks mild.

Ask whether the pattern fits hives, whether a medicine or infection could be involved, and what action plan to follow if swelling or breathing symptoms develop.