Warm urticaria: what to know

Hives are temporary raised areas that may feel itchy, sting, or burn. With a warmth trigger, symptoms may follow a hot shower, exercise, a warm room, heated clothing, or direct heat. The rash can affect the warmed area or appear more widely. Swelling around the eyelids, lips, hands, or feet may occur alongside welts; this deeper swelling is called angioedema. A photo and a note about the heat exposure can help a clinician recognise the pattern. Other causes of hives remain possible, so do not assume every heat-related rash is urticaria.

Move away from the heat source and cool the skin gently with a comfortable cool compress. Wear loose, breathable clothing and avoid rubbing or scratching, which can further irritate the skin. Keep a record of triggers, timing, body areas, medicines, and how long each episode lasts. A clinician may recommend an oral antihistamine for itch and welts, with the choice and dose matched to your health and other medicines. Do not apply ice directly to skin or start steroid tablets without medical advice.

Seek emergency help if hives or swelling occur with trouble breathing, wheezing, throat tightness, faintness, confusion, or swelling of the tongue. Arrange prompt medical review for rapidly spreading swelling, repeated episodes, severe discomfort, or symptoms involving the eyes or mouth. A rash that lasts, bruises, becomes painful, or leaves marks deserves assessment because it may not be ordinary hives.

Ask whether the pattern fits heat-triggered hives, whether another trigger should be checked, and which antihistamine is suitable with your current medicines. Ask what to do if swelling reaches your lips or throat and whether you need a written flare plan.