What should you know about hives from overheating?

Heat-related hives may be small, numerous bumps or larger joined welts. They can arise during exercise, a hot shower, fever, emotional stress, or a warm environment, and often improve after the skin cools. The rash may move or fade in one area while appearing elsewhere. Hives are the skin finding; the trigger may be heat, pressure, sweat, or another exposure rather than heat alone. See the overview of [Hives](/conditions/urticaria/) and the related symptom pages for [Itchy Skin](/symptoms/itchy-skin/) and [Skin Rash](/symptoms/skin-rash/).

Move to a cooler place, loosen tight clothing, and use a cool—not icy—cloth on the affected skin. Sip fluids if you can drink normally, pause strenuous activity, and avoid rubbing or scratching the welts. Record what happened before the flare, including exercise, heat exposure, food, medicines, and any new product. A clinician or pharmacist can advise whether an oral antihistamine is suitable; treatment information is available under [Antihistamine Treatment](/treatments/medical-dermatology/oral-antihistamine-therapy/). Do not start or stop prescription medicine without individual advice.

Seek emergency help immediately if hives occur with trouble breathing, wheezing, throat tightness, faintness, confusion, or swelling of the lips, tongue, or inside the mouth. These features can signal a severe allergic reaction. For facial or deeper swelling without breathing trouble, prompt medical assessment is still sensible; read about [Angioedema](/conditions/angioedema/) and [Skin Swelling](/symptoms/skin-swelling/). Arrange a medical review if episodes keep returning, last beyond a short flare, or make it difficult to sleep or exercise safely.

Could this be heat-triggered urticaria or another rash? Should I avoid particular exercise, showers, or medicines? Which antihistamine and dose are appropriate for me? What symptoms mean I should use an emergency plan?