Hives after a fever

Hives are raised, itchy patches that can appear and fade in different places. After a fever, they may be part of the immune response to an infection, including a viral illness. A medicine taken during the illness can also trigger them, so record every new drug, including pain relief and antibiotics. Hives do not identify one cause on their own. A rash that stays fixed in one place, becomes painful, forms blisters, or leaves bruising needs a clinician’s review because it may not be typical urticaria.

Keep the skin cool with loose clothing and a cool compress. Avoid hot showers, vigorous rubbing, and any suspected trigger until a clinician advises you. A pharmacist or doctor can recommend an antihistamine suited to the person’s age, pregnancy status, and other medicines. Keep drinking fluids after a fever and note when the rash began, how long each patch lasts, and what was taken beforehand. Do not restart a medicine that a clinician has identified as a possible trigger without advice. Depending on the other symptoms, the illness may relate to a common cold, COVID-19, chickenpox, or another infection.

Call emergency services for trouble breathing, wheezing, throat or tongue swelling, faintness, or rapidly worsening symptoms. Seek same-day medical advice for swelling around the eyes or mouth, repeated vomiting, a high or returning fever, marked drowsiness, or a rash with purple spots. Children with a new rash and poor drinking should be assessed promptly.

Ask: Could this be infection-related or medicine-related? Which treatment is suitable? What signs mean emergency care? Should any recently started medicine be recorded as a possible allergy?