Overview
Hives are raised, itchy welts on the skin that appear suddenly and can move around, fading in one spot and rising in another within hours. They are caused by the release of histamine in the skin, often as a reaction to food, medicine, infection or heat, though frequently no cause is found. Most bouts settle within a day or two and respond well to antihistamines. Rarely, hives come with dangerous swelling that needs emergency care.
Symptoms
- Raised, red or skin-coloured itchy welts
- Welts that change shape and location over hours
- Blanching (turning pale) in the centre when pressed
- Sometimes swelling of the lips or eyelids
- Itching that may be intense
When to see a doctor
See a doctor if hives keep returning for weeks, or urgently if there is swelling of the lips, tongue or throat, or difficulty breathing.
Emergency — call 108 or go to the nearest hospital
- Swelling of the tongue, lips or throat, difficulty breathing, wheezing or feeling faint — this is a severe allergic reaction, call 108 immediately
Causes
Histamine release triggered by foods, medicines, insect stings, infections, heat, cold or pressure — often no specific trigger is found.