What causes hives, and what can help?

Hives, also called urticaria, are raised itchy welts or wheals. They can be pink, red, skin-coloured or harder to see on darker skin. They may be small spots or join into larger patches, change shape and appear in different places over a few hours.

An individual wheal usually fades within minutes to 24 hours without leaving a mark, even while new wheals appear elsewhere. The whole episode can continue for days or weeks. Hives occurring on most days for six weeks or longer are described as chronic urticaria.

Deeper swelling under the skin is called angioedema and often affects the eyelids, lips, hands or feet. Tongue or throat swelling, breathing or voice change, persistent dizziness or collapse can be anaphylaxis and needs immediate first aid and 000.

Hives can follow a viral or other infection, a medicine, an insect sting or bite, or a true allergy. Physical factors such as heat, cold, pressure, rubbing, exercise, sweating or sunlight can also trigger or aggravate hives in some people.

A food allergy is more likely when hives start soon after a particular food and form part of a repeatable immediate reaction. Hives that recur for weeks are usually not caused by food allergy. Often no single trigger is found.

If new hives begin after a medicine, contact the prescriber or a pharmacist promptly, ideally before the next dose, for advice about what to do. Do not take another dose during an emergency reaction; call 000. Avoid broad food restriction, and do not deliberately retry a food that may have caused an immediate allergic reaction unless an allergy clinician has advised a supervised plan.

Cool the skin with a cool compress, a lukewarm shower and loose clothing unless cold is a known trigger for your hives. Avoid scratching where you can, and choose fragrance-free skin products if the skin is sensitive.

Avoid a known trigger when the link is clear, but do not assume every recent food, medicine or product caused the episode. Heat, alcohol, spicy food, pressure and some pain medicines can aggravate hives in some people, so note whether any factor repeatedly changes your symptoms.

Take clear photos when wheals are visible because they may fade before an appointment. Include one image showing the overall area and another showing detail, without sharing identifying body features unless they are relevant to care.

A pharmacist can discuss a non-drowsy antihistamine and check what is suitable with your age, pregnancy possibility, medicines and health conditions. Follow the label or clinician's instructions and ask when symptoms should be reviewed.

Treatment aims to reduce itch and new wheals; it does not prove the cause. Persistent or frequently recurring hives may need a planned treatment review rather than repeated changes or increasing treatment on your own.

Do not rely on an antihistamine for tongue or throat swelling, breathing difficulty, voice change, persistent dizziness or collapse. These can be signs of anaphylaxis and need immediate first aid and 000.

A HerDoc GP can review photographs, how long each wheal lasts, whether marks remain, possible exposures, infections, medicines and associated swelling or other symptoms. The GP can discuss treatment and whether local examination, testing or referral would add useful information.

HerDoc consultations are by phone. A local clinician may need to examine painful, bruising, blistering or persistent lesions, and an emergency reaction needs 000 rather than an online appointment. Photographs can support assessment but cannot confirm every cause or replace examination when texture, temperature or circulation matters.

Most short episodes of typical hives do not need allergy testing. Targeted testing may help when the history suggests a specific immediate allergy or when prolonged or unusual symptoms raise another question. Broad allergy panels can produce results that do not explain the hives.

Arrange GP review if hives are not settling, keep returning, disrupt sleep or daily life, or occur on most days for six weeks or longer. Bring photos and a list of treatments, medicines and patterns you have noticed.

Painful lesions, wheals that remain in exactly the same place beyond 24 hours, bruising or purple marks, high fever, bleeding into the skin or sore joints are not a typical simple-hives pattern and need prompt medical assessment.

Ongoing symptoms may need a treatment plan, medicine review or specialist assessment. Avoid restrictive diets and unvalidated allergy tests. If testing is needed, it should answer a specific clinical question.

The timing and appearance often provide more useful clues than a long list of possible allergens.

Anaphylaxis can occur with or without hives. Act on airway, breathing or circulation symptoms rather than waiting to see whether the rash spreads.

Further information about hives, recurring urticaria and anaphylaxis first aid is available from these health services.