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World Allergy Organization
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Disease Summaries

Urticaria and Angioedema

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Definitions

Urticaria is a skin rash, also called hives, or nettle rash, which is often accompanied by swelling and itching of the skin.

Angioedema (in the past this was called giant urticaria or angioneurotic edema) is a condition involving swelling in the deeper layers of the skin, caused by a build up of fluid leaking from thin-walled blood vessels. It can accompany hives or occur alone.

Symptoms

Hives are itchy and have a central, raised white wheal surrounded by an area of redness. Hives whiten if pressure is applied to the rash. The rash generally disappears within 24 hours.

Swelling of deeper layers of the skin, angioedema, is often seen with hives (click for picture). The redness that accompanies hives isn’t seen, but the swelling is very obvious. The swelling generally occurs on the fingers and toes, as well as areas of the head, neck, face, and, in men, the reproductive organs, and is often described as painful or burning.

Classification

Hives and angioedema are described by the length of time that symptoms last. A rash and/or swelling lasting less than six weeks is called acute hives/angioedema. Episodes that last more than six weeks are described as chronic hives/angioedema. The causes and the body’s reactions that lead to development of hives are different in acute and chronic hives/angioedema, and so treatment is also different.

Acute Hives

Acute hives can be divided into two general types, depending on the rate at which hives develop and the length of time the rash lasts. In one type, the rash lasts 1-2 hours; this is usually the type found in physically induced hives (see below). The second type can last as long as 36 hours; this is the type commonly seen in food or drug reactions.

Chronic Hives and Angioedema

Chronic hives and angioedema are diagnosed when hives and swelling are present for more than six weeks (click for picture). Before the diagnosis is made, it is important to make sure that what seems to be a long-lasting attack of hives is not really a series of short attacks occurring close together.

Chronic Idiopathic Hives and Idiopathic Angioedema

This is a common disorder, and the diagnosis of idiopathic hives and angioedema is made when no cause can be found. The skin symptoms may vary from severe to mild or may intermittently subside, and routine blood tests show no obvious abnormalities. Chronic hives does not appear to be a true allergic reaction, because IgE antibody is not involved, and no contact with an allergen is needed to bring on the symptoms.

Causes 

Allergic Hives

stinging insectAcute hives caused by an allergic reaction is a common condition in children and adults. When an allergen (for example, a food or insect sting) to which the person is allergic enters the bloodstream, it starts a series of reactions in the body’s immune system. These reactions lead to the release of histamine and other chemicals into the blood and can result in hives and/or other allergic symptoms. Common allergens that can cause acute hives include foods, drugs (particularly antibiotics such as penicillin), and venoms from the stings of insects such as bee, wasp, yellow jacket, hornet, or fire ant, but virtually any allergen has the potential to cause hives.

In general, if an allergen causes hives or swelling, it is usually eaten (food, drug taken by mouth) or injected (drugs, stings). Allergens that are inhaled tend to cause asthma or rhinitis and may contribute to the development of eczema in children.

latex glove If an allergen can penetrate the skin, hives will develop at the site of exposure. For example, contact hives may occur following exposure to latex gloves if sufficient latex penetrates through the skin.

Non-specific Causes

Acute hives can result from causes other than true (IgE-mediated) allergies. An example is exposure to certain dyes used in X-ray procedures, which can cause a whole-body reaction called anaphylaxis which includes hives. Acute viral illnesses in children can be associated with hives which last a few weeks and then spontaneously subside. This usually occurs in association with the symptoms of a common cold, sore throat, or bronchitis. If these patients are given an antibiotic, the cause of the hives becomes confused, because a reaction to the antibiotics may be causing the hives. If penicillin or related antibiotics have been taken, the doctor may perform an allergy skin test, or blood tests for IgE antibodies against the antibiotic, because it is important to know whether or not the patient has had an allergic reaction to the antibiotic. Hepatitis B, glandular fever and intestinal parasites may all be associated with the development of hives.

Hives and angioedema can also result from drug treatments. These include codeine and opiate-derived medications, as well as aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs). The responses to NSAIDs can be life-threatening because the angioedema can lead to serious swelling of the tongue and/or throat. Drugs used to treat high blood pressure, known as ACE inhibitors, can cause recurrent episodes of angioedema.

If chronic hives do not appear to be associated with any other disease, and are not due to one of the physically induced urticarias described below, they are called idiopathic, that is, of unknown origin. Research suggests that in 35-45% of patients with idiopathic hives the cause may be autoimmunity – that is, the patient’s immune system working against itself. These autoimmune types of hives are not serious and usually respond to treatment with antihistamines.

Physical Hives

Hives and/or angioedema can be caused by environmental factors, such as a change in temperature, or pressure on the skin. Two rare causes of hives are exposure to sunlight, or contact with water.

Cold-dependent Disorders

Cold urticaria is the rapid onset of itching, redness, and swelling of the skin after exposure to cold. The symptoms of cold urticaria may occur for the first time some weeks after a viral infection, and only affect those parts of the body that have been exposed to cold. To test for this, an ice-cube can be placed on the forearm for 4-5 min. A positive reaction leads to a hive in the shape of the ice cube within 10 minutes after the source of cold has been removed (click for picture).

Cold urticaria can be restricted to certain areas of the body, for example, where there has been a cold injury, or at the sites of allergen immunotherapy (desensitization) injections, or insect bites. Another skin condition which is related to cold is cold-dependent dermatographism where hives form if the skin is scratched and then chilled (click for picture).

Exercise-induced Disorders

Cholinergic or generalized heat urticaria is the onset of small wheals surrounded by a large area of redness, associated with exercise, hot showers, sweating and anxiety (click for picture). The rash first appears on the neck and upper chest, giving a flushed appearance. This is accompanied by intense itching. The rash spreads gradually to the face, back, and extremities, and the wheals increase in size. In some people the hives join up and resemble angioedema. Watering eyes, increased saliva production and diarrhea can occur at the same time. Cholinergic urticaria is the only form of hives that can be caused by emotional responses.

Exercise-induced anaphylaxis was first described in a series of people who experienced combinations of itching, skin rash, swelling, wheezing, and low blood pressure as a result of exercise. The hives seen with exercise-induced anaphylaxis are large, in contrast to the small hives seen in cholinergic urticaria. A type of exercise-induced anaphylaxis has been described that is related to food, and occurs only if exercise takes place 5-24 hours after eating a food to which the individual is allergic.

Pressure-induced Hives/Angioedema

Pressure-induced hives/angioedema occurs 4-6 hours after pressure has been applied to the skin. There may be either a rash or swelling, or both, occurring around tight clothing; the hands may swell with activity such as hammering; foot swelling is common after walking; and buttock swelling may occur after sitting for a few hours.

Solar Urticaria

sun Solar urticaria is a rare disorder in which brief exposure to light causes the development of hives within 1-3 minutes. It starts with itching about 30 seconds after exposure to sunlight, and is followed by swelling and redness of the light-exposed area. The symptoms usually disappear within 1-3 hours.

Aquagenic Urticaria

Individuals develop small wheals after contact with water, regardless of its temperature.

Association with Autoimmune Thyroid Disease

Patients with chronic hives have an increased frequency of Hashimoto’s Disease (thyroiditis), and tests of thyroid function and thyroid antibody levels can be performed to see if this is responsible for the skin symptoms.

Treatment 

Treatment of Acute Hives and Angioedema

Acute episodes of hives and/or swelling can be treated with antihistamines, and 1% menthol in aqueous cream may help control itching. If the allergens causing hives and/or swelling have been identified, either from the description of the attacks, or by blood testing for specific IgE antibodies, allergen avoidance will help to prevent further attacks. If the hives or swelling have resulted from taking medications, the patient’s physician will be able to identify different types of medications for future treatment. Tightly-fitting clothes should be avoided, as wheals often occur in areas of pressure. As the itching associated with hives can be more severe in warm conditions, it may help to keep the home cool, and to ensure that the bedroom is not too hot. Urticaria and angioedema can be symptoms of a systemic reaction called anaphylaxis and may require urgent administration of intramuscular epinephrine (adrenaline).

Treatment of Chronic Hives

Antihistamines are valuable in the treatment of chronic hives and are more effective on the itching than the wheals. If the symptoms continue when the maximum recommended amount of antihistamines has been given, a short course of corticosteroid tablets may be helpful.

Epidemiology: Who Develops Urticaria and Angioedema, and Why?

Urticaria and angioedema are thought to affect 20% of the population at some time during their lifetime. Hives alone or associated with the swelling of angioedema are more common in women, while angioedema alone, in the absence of hives, is more common in men. Less than 10% of hives develop into a chronic problem. Very often an attack of hives occurs without anyone understanding why it has happened, with little or no risk of the symptoms recurring.

Links to Additional Information on Urticaria and Angioedema

Allergy Society of South Africa (ALLSA)
www.allergysa.org. Go to online literature, then to skin, then to urticaria and cold urticaria.

American Academy of Allergy, Asthma and Immunology (AAAAI)
www.aaaai.org/public/publicedmat/advocate/2000/summer/ what_is_urticaria.stm
www.aaaai.org/public/publicedmat/tips/allergicskinconditions.stm
www.aaaai.org/public/publicedmat/tips/spanishtips/ condiciones_alergicas_de_la_piel.stm  (in Spanish)

American College of Allergy, Asthma and Immunology (ACAAI)
www.acaai.org/allergist/allergies/Types/skin-allergies/hives/Pages/default.aspx

Australasian Society of Clinical Immunology and Allergy (ASCIA)
www.allergy.org.au/aer/infobulletins/urticaria.htm

Glossary of Terms Used

Allergen: any protein which can cause an allergic reaction in a person who is sensitized to it

Acute: short lasting

Anaphylaxis: an allergic or non-allergic reaction involving the whole body

Angioedema: swelling of the deep layers of the skin

Cholinergic: relating to the nervous system

Chronic: long-lasting

Dermatographism: the ability to "write" a white line on the skin by scratching it

Generalized: occurring all over the body

Hives: commonly used name for urticaria

Idiopathic: of unknown origin

IgE-mediated: a reaction of the immune system resulting from an allergen entering the blood-stream and reacting with Immunoglobulin-E antibodies in the blood

Localized: occurring in only one area of the body

Physically-induced: caused by exercise or an external, non-allergic, source

Urticaria: hives, nettle rash

Wheals: white bumps/blistering of the skin