Hives (Urticaria)

How urticaria works

Mast cells are immune cells that sit in the skin around blood vessels. When activated, they release histamine and other chemicals. Histamine makes small vessels leak fluid into the upper skin, creating a welt, and stimulates nerves, causing itch. When the leak occurs deeper in the skin or mucous membranes, the result is angioedema.

Mast cells can be activated by:

• IgE allergy (foods, stings, drugs) in some acute cases
• Autoantibodies against IgE or its receptor (autoimmune chronic urticaria)
• Direct activation by drugs such as opioids, contrast dye and NSAIDs
• Physical stimuli such as cold, pressure, heat or friction
• Infections

Types of urticaria

Inducible (physical) urticarias

• Symptomatic dermographism: welts along scratch lines; the most common type
• Cold urticaria: hives on cold exposure; swimming in cold water can cause collapse
• Cholinergic urticaria: tiny itchy bumps with sweating, exercise, hot showers or stress
• Delayed pressure urticaria: deep painful swelling hours after pressure (bag straps, tight belts, standing)
• Solar, heat, aquagenic and vibratory urticaria: rarer types

Who gets chronic urticaria

Chronic spontaneous urticaria affects up to about 1% of people at some point, women about twice as often as men, usually between ages 20 and 40. It is linked to autoimmune thyroid disease (Hashimoto's thyroiditis) and other autoimmune conditions. Stress, infections, NSAIDs and alcohol can trigger flares. Food allergy is rarely the cause of chronic hives, although many people suspect it.

Symptoms

• itchy welts lasting less than 24 hours each
• angioedema in about 40% of people with chronic urticaria, most often lips, eyelids, hands and feet, lasting up to 72 hours
• flares often worse in the evening
• sleep disturbance and impact on work and mood

What hives look like and how to manage a sudden outbreak is covered on our page about hives as a symptom.

Diagnosis

Acute urticaria

No tests are usually needed. If a food, sting or medicine allergy is suspected, an allergist may arrange skin-prick or specific IgE tests.

Chronic urticaria

International guidelines recommend a limited set of tests:

• full blood count with differential
• C-reactive protein or ESR
• in many cases, total IgE and thyroid antibodies (anti-TPO), which can help predict treatment response

Further tests depend on history:

• Provocation tests for inducible urticaria (an ice cube test for cold urticaria, a dermographometer for dermographism)
• Skin biopsy if welts last more than 24 hours or bruise (possible urticarial vasculitis)
• Complement C4 and C1 inhibitor if there is angioedema without hives (hereditary angioedema does not respond to antihistamines)
• Tryptase if mastocytosis is suspected

A daily urticaria activity score (UAS7) diary helps track severity and response.

Treatment

Step 1: Daily non-drowsy antihistamine

Second-generation H1 antihistamines (cetirizine, levocetirizine, loratadine, desloratadine, fexofenadine, bilastine) taken every day, not just when hives appear.

Step 2: Higher-dose antihistamine

If not controlled after 2 to 4 weeks, guidelines support increasing the antihistamine up to 4 times the standard dose, under medical supervision. This controls many people who do not respond to standard doses.

Step 3: Omalizumab

Omalizumab, an injectable anti-IgE biologic given every 4 weeks, controls chronic spontaneous urticaria in a majority of antihistamine-resistant patients. Newer biologics and oral treatments are emerging for resistant cases.

Step 4: Cyclosporine

An immune-suppressing medicine for severe cases not controlled by omalizumab, with monitoring of blood pressure and kidney function.

Other measures

• Short courses of oral steroids may be used for severe flares, but not long-term because of side effects.
• Avoid triggers: NSAIDs and aspirin, alcohol, overheating, tight clothing for pressure urticaria.
• ACE inhibitors (blood pressure medicines) can cause angioedema; your doctor may switch them.
• Epinephrine auto-injector for people with cold urticaria at risk of systemic reactions or any history of anaphylaxis.

Outlook

Acute urticaria nearly always resolves within weeks. Chronic spontaneous urticaria resolves on its own in about half of people within 1 to 5 years, though it can recur. With modern treatment, most people achieve good control. Urticaria itself does not damage the skin or internal organs.

Frequently asked questions

What is the difference between acute and chronic urticaria?

Acute urticaria lasts less than 6 weeks and is often triggered by an infection, food, medicine or sting. Chronic urticaria lasts 6 weeks or longer, with hives on most days. Chronic urticaria is usually not caused by allergy and often has an autoimmune basis.

What causes chronic hives?

Most chronic hives are spontaneous, meaning no external trigger is found. Many cases involve autoantibodies that activate mast cells, and chronic hives are linked to autoimmune thyroid disease. Physical triggers such as pressure, cold or heat cause inducible types. Food allergy is a rare cause.

Is urticaria an autoimmune disease?

Chronic spontaneous urticaria often is. In many people, the immune system makes antibodies against IgE or its receptor on mast cells, triggering histamine release. People with chronic hives have higher rates of thyroid autoimmunity. Acute urticaria is usually not autoimmune.

Can urticaria be cured?

Acute urticaria usually goes away completely. Chronic urticaria has no immediate cure, but about half of cases resolve within 1 to 5 years, and treatment with daily antihistamines or omalizumab controls symptoms in most people while it runs its course.

Is it safe to take antihistamines every day for hives?

Yes. Non-drowsy second-generation antihistamines are considered safe for long-term daily use and are the recommended first treatment for chronic hives. Higher doses should only be used on medical advice. Older sedating antihistamines are not recommended for regular use.