Common causes of hives

A hive is a raised, often itchy area that may appear suddenly and fade from one spot before showing up elsewhere. Individual welts can change shape and size over a short time. Hives are also called urticaria or a nettle rash.

An allergic reaction may follow a food, insect sting, latex, or another substance. A medicine can also cause hives, including a medicine that was previously tolerated. Do not stop a prescribed medicine without getting clinical advice, but record its name and when the rash began.

Viral or other infections may produce hives, especially when a rash appears with feeling unwell. Physical triggers can include heat, cold, exercise, sweating, tight clothing, pressure from a strap, or rubbing and scratching. Stress may worsen symptoms for some people, but it does not prove that stress is the cause.

When welts continue or return over a longer period, an immune system condition may be involved, although testing does not always identify a specific trigger. Hives can occur with deeper swelling of the lips, eyelids, hands, feet, or throat; this is known as angioedema. Read more about [Hives](/conditions/urticaria/) and [Angioedema](/conditions/angioedema/).

Note what happened before the outbreak: foods, medicines, new products, illness, exercise, temperature changes, pressure, and insect contact. Photographs can help because a hive may disappear before an appointment. Wear loose clothing, avoid hot showers, and use a cool compress if that feels soothing.

A clinician or pharmacist can advise whether an oral antihistamine is suitable and how to use it safely. Some people need a different treatment when symptoms are persistent; oral corticosteroids should only be used when prescribed. Avoid repeatedly testing a suspected food or medicine on yourself.

Call emergency services immediately if hives occur with trouble breathing, wheezing, throat tightness, difficulty swallowing, faintness, confusion, or sudden swelling of the tongue or mouth. These can signal a severe allergic reaction, which may worsen quickly.

Seek prompt medical advice for swelling around the eyes or lips, repeated episodes, a rash that lasts in one place rather than moving, bruising or pain, fever, or symptoms after starting a medicine. Arrange a review if hives keep returning or interfere with sleep and daily activities. Associated [Itchy Skin](/symptoms/itchy-skin/), [Skin Rash](/symptoms/skin-rash/), or [Skin Swelling](/symptoms/skin-swelling/) can be documented for the clinician.

Ask which triggers fit the timing and appearance of your welts, whether any medicine or infection could be contributing, and whether you should keep a symptom and exposure diary. Ask what to do if swelling affects your mouth or throat, and which treatment is appropriate for your other medicines or health conditions.