When your body heats up, hives may appear as itchy small welts or larger raised patches. Cooling down and checking for airway symptoms are sensible first steps.

Heat, exercise, fever, hot showers, and emotional stress can all raise skin temperature. In some people this provokes a form of inducible urticaria; in others, hives during a fever occur alongside an infection or medicine reaction. The rash itself does not identify the cause. Welts may fade in one area and arise elsewhere, while deeper swelling can affect the eyelids or lips.

Move to a cooler place, loosen tight clothing, and use a cool damp cloth rather than ice directly on skin. Drink fluids if you can and avoid hot showers, strenuous activity, and alcohol until the episode settles. Record your temperature, timing, recent illness, medicines, and what the welts looked like. A pharmacist or clinician can advise on oral antihistamine treatment. Do not change prescribed medicine without advice.

Seek emergency help for swelling of the tongue, lips, mouth, or throat, trouble breathing, wheezing, faintness, confusion, or difficulty swallowing. Get prompt medical advice when fever is persistent, the rash is painful rather than itchy, bruises, blisters, or does not fade with pressure, or the episode follows a new medicine. Arrange review for repeated heat-related outbreaks.

Ask what pattern best fits your symptoms, whether a medicine or illness could be contributing, which treatment is suitable for you, and which warning signs should prompt emergency action.