Allergy hives: what they mean and what to do

Individual welts may change shape, fade and reappear elsewhere. Their colour can be pink or red, or close to the surrounding skin tone. Treatment depends on severity, possible triggers and whether deeper swelling is present.

Hives, also called urticaria, develop when skin cells release substances including histamine. Food, medicine, an insect sting or contact with latex can trigger an allergic episode. Heat, cold, pressure, exercise, infection and sometimes no identifiable cause can produce a similar rash.

Deeper swelling of the lips, eyelids, hands or feet can accompany hives and is called angioedema. The location and associated breathing symptoms matter more for urgency than the size or number of welts.

Stop contact with a suspected new product or food, but do not stop a prescribed medicine without medical advice unless an emergency clinician directs you. Keep cool, wear loose clothing and avoid scratching; a cool compress may settle the itch.

A clinician or pharmacist can advise whether an oral antihistamine is suitable, especially for a child, during pregnancy, or when other medicines or health conditions are involved. Record recent foods, medicines, infections and exposures, and photograph changing welts for the appointment.

Call emergency services now for trouble breathing, wheezing, throat tightness, faintness, confusion, or swelling of the tongue or throat. Use a prescribed adrenaline auto-injector immediately if your emergency plan says to do so, then obtain emergency care even if symptoms improve.

Arrange a medical assessment when hives keep returning, persist, follow a new medicine, or come with fever, bruising, joint pain or welts that stay fixed and painful. These features can point away from straightforward short-lived hives.

Ask whether the pattern fits hives, whether any medicine or exposure should be avoided, which antihistamine is appropriate, and what symptoms should trigger an emergency plan. Mention lip or eyelid swelling, breathing changes and every medicine or supplement taken before the outbreak.