Hives (urticaria): causes, how long they last and treatment

You woke up with raised, itchy patches on your arms that were gone by lunchtime, only for new ones to appear on your legs that evening. Or it has been happening on and off for two months, and nobody can tell you why.

That shifting, come-and-go rash is hives, also called urticaria. Roughly one in five people get it at some point. The welts can be tiny or the size of a hand, appear anywhere on the body and move around over hours. Both short-lived and long-running hives respond well to treatment once the right antihistamine plan is in place.

For a new rash, a private GP appointment at our Harley Street clinic is £150, seven days a week, with antihistamines prescribed at the visit. For hives that keep coming back, our allergy clinic with consultant immunologist Dr Scott Pereira starts with a £250 consultation.

What causes hives?

Hives appear when mast cells in the skin release histamine, which makes small blood vessels leak fluid into the skin. Acute hives are often set off by a viral infection, particularly in children. Foods such as shellfish, nuts and eggs, medicines such as anti-inflammatory painkillers and antibiotics, insect stings and latex are other common causes. Some plants, chemicals and even cold water can do it too.

Physical triggers are grouped as inducible urticaria. They include pressure or scratching (dermatographism, where a line drawn on the skin rises into a welt), heat, sweating and exercise, cold and sunlight. They account for a large share of long-running cases.

In about half of chronic cases, no outside trigger is found. This is chronic spontaneous urticaria, and it is thought to be autoimmune: the body's own antibodies switch on the mast cells. That is why allergy tests often come back normal in chronic hives, and why stress or an infection can trigger a flare without being the cause.

How long do hives last?

Types of hives at a glance

Each welt usually fades within 24 hours without a mark, even if new ones keep arriving elsewhere. If a single patch lasts longer than a day, leaves a bruise or is painful rather than itchy, mention it to the doctor, as it may be a different rash.

Hives can appear on the hands, legs, face or anywhere else. On the face, deeper swelling of the eyelids or lips is often angioedema, which is covered below.

Angioedema: swelling with or without hives

Angioedema is swelling in the deeper layers of the skin, most often of the lips, eyelids, tongue or genitals. It often comes with hives, but it can happen on its own. When it appears without hives, the cause is often not allergic. ACE inhibitors, a common blood pressure medicine, are the best known example, and antihistamines may not help that kind of swelling. Rarely, it runs in families (hereditary angioedema).

Call 999 if hives or swelling come with swelling of the tongue, lips or throat, difficulty breathing or wheezing, feeling faint or dizzy, or a racing heart. These can be signs of anaphylaxis. If you carry an adrenaline auto-injector, use it and still call 999.

Hives treatment

First-line treatment is a non-sedating antihistamine such as cetirizine, loratadine or fexofenadine. They block histamine and ease itching and swelling, and they work best taken every day rather than only when a rash appears.

If a standard dose is not enough, BSACI guidelines support increasing it up to four times the normal dose before moving on. This is safe for most adults, but agree it with your doctor so they can follow your response. A short course of steroid tablets (prednisolone) may be used to settle a severe flare. Long-term steroids are avoided because of their side effects.

For severe chronic spontaneous urticaria that has not responded to antihistamines, NICE recommends omalizumab, an injection given as an add-on for adults and young people aged 12 and over. Dr Pereira offers it in our allergy clinic at £500 per visit when the licensed criteria are met. This is the main reason to see a specialist when tablets are not controlling things. A GP here can also refer you to a dermatologist when your skin needs a specialist opinion.

Day to day, cool compresses and loose clothing help, and keeping a symptom record often reveals a pattern you would otherwise miss.

Which tests help with hives?

Short-lived hives rarely need tests. If hives last longer than 6 weeks, blood tests can rule out an underlying condition: a full blood count, inflammation markers (CRP or ESR) and thyroid function. Thyroid autoimmunity is found in 10 to 27% of people with chronic urticaria, and our guide to thyroid blood tests explains the profiles.

Allergy testing is most useful when there is a clear link between hives and a food, animal or something in your surroundings. Skin prick testing costs £450, including the consultation and up to eight allergens, with results discussed in the same appointment. The ALEX3 blood test screens more than 290 allergens from one sample for £413.75, with results in about 5 working days. Our guide to choosing an allergy test compares the two.

Getting hives seen at 117a Harley Street

For a new outbreak, a GP appointment (£150) covers an examination, a treatment plan and an antihistamine prescription, seven days a week. For hives lasting more than 6 weeks, or swelling that keeps returning, book an allergy consultation with Dr Scott Pereira, consultant immunologist, for £250. He works on Tuesdays from 14:00 to 17:30, blood tests can be done at the clinic, and he decides with you whether testing or treatment such as an injection is the next step.

If wheeze or a cough comes with your allergies, our guide to asthma tests and inhalers may help.