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 an abnormal immune response. While this typically occurs as a result of an allergy to a food or medicine, there are non-allergic causes. Symptoms may come and go quickly or be longer-lasting. 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.

Verywell / Emily Roberts

Urticaria Symptoms

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

The hives will appear as raised welts (wheals or weals) and will invariably be itchy, some more than others. They can vary in shape and size but will have a clearly defined border. When pressed, the center will "blanch" (turn white).

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 to 48 hours. Others may take days or weeks before they fully resolve. 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, blistering, 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 Hives on leg.

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.

Certain chronic forms of urticaria are believed to be triggered by an autoimmune response. Others are entirely idiopathic (meaning of unknown origin).

Allergy-Induced Urticaria

Allergy-induced urticaria is caused when the immune system responds abnormally to an otherwise harmless substance and releases a chemical known as histamine into the bloodstream.﻿﻿ Histamine is an inflammatory substance that causes the symptoms of allergy, affecting not only the respiratory and gastrointestinal tract but the skin as well.

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

Chronic Idiopathic Urticaria

Chronic urticaria is more often idiopathic and may be induced by stress or other physical stimuli.﻿﻿ While the exact pathway of the condition is unknown, it is believed that the activation of autoantibodies (immune proteins that target the body’s own cells) may also trigger the release of histamine and other pro-inflammatory compounds.

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

In addition to stress, common physical triggers include exposure to cold, heat, sunlight, pressure, vibration, water, and friction. Certain types of exercise-induced urticaria occur only in tandem with a food allergy.

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 doctor 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). The maximum score of 6 indicates a serious eruption in need of aggressive treatment.

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 radioallergosorbent assay test (RAST) are two of the most common forms of 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 radioallergosorbent assay test (RAST) are two of the 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.

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 really 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 may only require a wet, cool compress to ease the itch and swelling.

Treatment for hives that don't resolve naturally depends on the cause and symptoms experienced. Some cases may take up to several weeks and require oral antihistamines to help alleviate the symptoms. Over-the-counter antihistamines such as Allegra (fexofenadine), Claritin (loratadine), and Zyrtec (cetirizine) usually provide ample relief.

Stronger antihistamine drugs may be obtained by prescription.﻿﻿

If antihistamines alone are able to provide 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 the itching and swelling if antihistamines don't work. ﻿ ﻿

﻿ Leukotriene modifiers like Accolate (zafirlukast) and Singulair (montelukast) are commonly used to treat asthma but can also relieve certain forms of chronic idiopathic urticaria. ﻿ ﻿

﻿ 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 in treating chronic forms of urticaria that have not responded to other therapies. ﻿ ﻿

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 doctor for a referral to an allergist who can perform tests to pinpoint the cause. If an allergy trigger is found, a series of allergy shots can be given to gradually desensitize you to its effect.

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.