What Is Urticaria (Hives)?

Urticaria (hives) usually starts with a red, itchy patch of skin and develops into a raised welt with clearly defined borders. It is caused by the release of histamine and other allergic chemicals from mast cells and basophils. While this may occur as a result of an allergy to a food or medicine, there are often non-allergic causes.

Symptoms may come and go quickly or they can be long-lasting. The appearance may be enough for diagnosis, but chronic cases may require allergy testing, a physical challenge, or other tests. Antihistamines are typically used to treat urticaria, although H2 blockers, corticosteroids, antidepressants, and anti-asthma drugs may also be prescribed.

Urticaria Symptoms

Urticaria can affect people of any age and may develop on any part of the body, including the palms and soles.

Symptoms are commonly confused with those of other conditions, but close attention to these defining factors can help distinguish urticaria.

Most hives are acute and self-limited, resolving on their own within 24 hours. Others may take days or weeks before they fully resolve. Hives that last longer are associated with more serious conditions, such as urticarial vasculitis.

During this time, it is not uncommon for the hives to disappear and reappear. Urticaria may sometimes be accompanied by a deep-seated swelling of tissue known as angioedema, most commonly affecting the face, lips, tongue, throat, or eyelids.

Chronic hives can persist for months or even years and may be triggered by stress, heat, cold, and other physical triggers.

Urticaria differs from eczema (atopic dermatitis) in that eczema is characterized by dryness, crusting, cracking, oozing, or bleeding. Hives are not typically described in these ways.

This photo contains content that some people may find graphic or disturbing.

See Photo

Causes

Broadly speaking, all forms of urticaria are a result of an abnormal immune response. While an allergy is the most common example, it is not the only cause.

Allergy-Induced Urticaria

Allergy-induced urticaria occurs when the immune system responds abnormally to an otherwise harmless substance and releases a chemical known as histamine into the bloodstream.

Histamine causes vasodilation (widening of the blood vessels) and movement of fluid from the blood vessels into the tissues, producing hives or angioedema. This leads to the symptoms of allergy, affecting the respiratory system, gastrointestinal tract, and skin.

Common triggers of allergy-induced urticaria include food (including shellfish, eggs, and nuts), drugs (including aspirin and antibiotics), and insect bites and stings (especially bees and fire ants).

Chronic Idiopathic Urticaria

Chronic urticaria is often idiopathic and may be worsened in times of stress. The exact pathway of the condition is unknown. In some patients, autoantibodies (immune proteins that target the body's own cells) are found in blood, but these autoantibodies are not necessarily disease-causing. Testing for anti-thyroperoxidase antibodies may be performed for chronic urticaria.

While the instigating cause of chronic urticaria may be different ​from allergy-induced urticaria, the outcome will be the same (albeit longer-lasting). Women tend to be affected more than men.

Other Causes

Infections and diseases like hepatitis, chronic kidney disease, lymphoma, and any number of autoimmune disorders (including lupus, Hashimoto's thyroiditis, and rheumatoid arthritis) may also manifest with acute or chronic hives.

Diagnosis

Urticaria can usually be diagnosed based on a review of your medical history and the characteristic appearance of the rash. Lab tests and imaging are generally not required unless an underlying cause is suspected, such as cancer.

The severity of an eruption can be classified based on an assessment tool called the urticaria activity score (UAS). For this, a patient subjectively rates the two primary symptoms—the wheals and the itchiness (pruritus)—on a scale of 0 (low disease activity) to 3 (severe disease activity). Having a maximum score of 6 often means that a patient requires further treatment, particularly if the symptoms are chronic.

If further testing is needed, it may involve one of the following:

• Allergy testing may be recommended if you’ve had a severe hypersensitive reaction to food, medications, or an insect sting. A skin test or a specific IgE test are the two most common forms of allergy testing.
• Physical challenge tests are used to confirm that your chronic hives are physically induced. This involves the application of the suspected stimuli—such as ice, heat, vibration, light, or friction—to the skin. Exercise testing may also be used.
• Skin biopsy (the removal of a tissue sample for lab evaluation) is only indicated if the hives fail to improve and no other cause can be found. Unless there is some unusual explanation for the wheals, a biopsy of a hive will usually not reveal anything abnormal.

Treatment

Most acute hives will resolve on their own within a few days and the itching and swelling may be eased with a wet, cool compress.

 Stronger antihistamine drugs may be obtained by prescription.

If antihistamines are adequate for providing relief, other drugs may be added or substituted, particularly if the cause is non-allergic.

Among them:

• H2 blockers, such as Pepcid (famotidine) and Tagamet (cimetidine), can be used in combination with antihistamines to reduce vascular swelling.
• Corticosteroids, like Prednisone, can dampen the immune response and quickly reduce itching and swelling. While this can be useful for a few days, it is generally not recommended long-term due to the potential for significant side effects.
• Leukotriene modifiers like Accolate (zafirlukast) and Singulair (montelukast) are commonly used to treat asthma but are also used off-label to treat certain forms of chronic idiopathic urticaria that have not improved with antihistamines alone.
• Doxepin is a tricyclic antidepressant that also acts as a powerful antihistamine when used in low doses.
• Xolair (omalizumab) is an injectable monoclonal antibody that is effective for treating chronic forms of urticaria that have not responded to antihistamines. Xolair is also approved for reducing allergic reactions for those with food allergies.

A Word From Verywell

While hives can be unsightly and uncomfortable, they usually aren't serious. However, if they start to interfere with your quality of life, ask your healthcare provider for a referral to an allergist who can perform tests to pinpoint the cause.

In rare cases, hives may develop as part of a potentially life-threatening allergy known as anaphylaxis. If your hives are accompanied by facial swelling, difficulty breathing, rapid heartbeat, vomiting, and/or confusion, call 911 or have someone rush you to the nearest emergency room. If left untreated, anaphylaxis can lead to shock, coma, heart or respiratory failure, and death.