Allergy/Asthma Information Association

Hives (Urticaria)

Hives are a common occurrence, affecting up to 25% of the population at least once in their lives. They can be short term, lasting only a few days to six weeks, but they can be chronic and last for months or years. Chronic hives can be especially frustrating for patients. They may or not be related to an allergy. In some cases the cause is never identified.

There are three principal classifications:


Acute hives can appear at any age, but they are most commonly seen in young adults. The rash has very itchy red areas with white raised central circles that resemble mosquito bites. If the welts grow very large, spreading and joining together or swelling downward deep into body tissue, then they are known as giant hives or angioedema. Angioedema is painful and unsightly, but it is not as itchy. With angioedema the eruptions become large enough to cause swelling of the eyelids, tongue, mouth, hands or feet. In severe cases, hives can be accompanied by other symptoms such as difficulty in breathing, difficulty swallowing, digestive upsets and fever. Hives can occur internally to produce swelling of internal organs. .

Hives can be caused by an allergic reaction to foods, drugs, insect bites, infections or substances which can cause other allergic reactions. However not all cases are caused by allergy; frequently they are caused by viruses. It can sometimes be extremely difficult to find the cause. Triggers include medications, food, viruses, latex, heat, cold and direct exposure to sun. If the cause is known, the trigger should be avoided.

Since hives can come and go so swiftly, a very significant percentage of cases are never accurately diagnosed. The hives can appear and disappear without any explanation of what caused them or cured them. Skin testing may be used in finding the source of infrequent hives; a detailed history is usually more rewarding. The patient can record everything that was ingested or touched for the 24 hours prior to the outbreak and bring this to the physician.

Treatment of acute hives:

  1. Avoidance: If the cause is found, then it should be removed from the environment or diet.
  2. Medications: Topical ointments can be applied to the skin to relieve the itch. Antihistamines will reduce the itching and swelling. Cortisone drugs used as an ointment or given by mouth may be needed.
  3. Immunotherapy: Allergy shots help only if a person has hives because of what they breathe. These people can be successfully desensitized. Cross reacting proteins from inhalants that are also found in foods can help drop the degree of reactivity to those foods.

Hives can look ugly and are unbelievably itchy, but they are not in themselves dangerous. However, if you have hives and other symptoms such as dizziness, vomiting, diarrhea, difficulty in breathing, difficulty swallowing or faintness, these are signs and symptoms of a much more serous reaction - anaphylaxis. Anaphylaxis is life-threatening! If you experience hives plus one or more of these other symptoms soon after eating or being injected with a substance that you do not usually use, OBTAIN MEDICAL HELP IMMEDIATELY.


When a person has had hives for over six weeks, they are termed chronic urticaria. Many experts believe that acute and chronic urticaria are no different except for duration. Some studies indicate that allergy is less likely to be an underlying factor in chronic urticaria. Since in 80 per cent of the cases of chronic urticaria the underlying cause is never found, not many conclusions can be made.

Discovering the exact cause of chronic urticaria is often extremely difficult. If the hives occur daily, they are most likely caused by something that you are exposed to daily. In that case, it is easier to see the cause/effect relationship. Sometimes it is several hours after exposure before the itching begins. In that case, some real detective work will be needed to find the culprit. These are the things to consider in order of importance: foods, drugs, infections, inhalants, and psychological factors.

To diagnose chronic hives the doctor will first make sure that the hives are not caused by infection or an underlying disease state. However, in the evaluation of patients with chronic urticaria, it is their history which is the most important diagnosis tool. The physician will look for clues regarding drug or chemical exposure, changes in dietary habits, changes in personal habits, alterations in residence or place of employment. She/he will also look for a pattern such as: Is there a relationship to eating? Does the patient wake-up with hives? Are they as likely to occur at home as at work/school? Are weekends or weekdays different in any way? The physician will often place a patient with chronic urticaria on a diet to see if elimination of the hive-trigger will bring relief. It is important to see a doctor before going on an elimination diet. Systemic diseases should be ruled out with this appointment. Sometimes these diseases can cause hives that are painful or burning in nature.


Typically, acute and chronic display round or oval hives, occur over virtually any part of the body and last for hours or days. There are others forms of urticaria which show up in lines or odd shapes, appear on specific parts of the body and appear then disappear within two hours. This is urticaria which is triggered by a physical cause. There are several possible causes:

  1. Pressure Urticaria
    Pressure hives produces deep and painful local swelling. The swelling can occur immediately or several hours later. This type of urticaria can be triggered by prolonged sitting. It is also triggered but the wearing of tight clothing and consequently is seen in areas such as the waist/belt line, under elastic bands such as panties, socks or wristbands. Choosing appropriate clothing and/or taking regular breaks from sitting, usually controls pressure urticaria. If medication is needed, steroids are usually administered for a short time.

  2. Cold-induced Urticaria
    Cold-induced Urticaria is a disorder in which hives occur within minutes of being exposed to the cold or appear as a result of the effects of warming. Total body exposure to cold, such as swimming in frigid water can result in a drop in blood pressure, fainting, shock and drowning.

  3. Dermographism
    Dermographism literally means skin writing. Scratching the skin will produce a raised mark and redden the surrounding skin. It is easy to test. Simply use a moderately sharp object, such as a fingernail or a key, and run it over the skin. If a recognizable patter is used in testing, such as a name or the game of X’s and O’s, it is a form of physical urticaria which is easily identified.
    This phenomenon usually occurs only in young adults and gradually disappears. An antihistamine will alleviate any associated itchiness.

  4. Solar Urticaria
    In this rare form of physical urticaria, hives occur after exposure to the sun or to certain artificial light sources. It is believed that the condition is an allergic reaction to an antigen formed by the interaction of light waves on the skin. Antihistamines are helpful to relieve the itch.

  5. Heat Urticaria
    There are two forms of heat urticaria. The more common form is also called cholinergic urticaria or generalized heat urticaria. In this form, it occurs when the body temperature is raised such as in a hot bath or shower, from a fever or exercise. The outbreak begins with a few small hives and gradually become more widespread. If the reaction is very severe, the wheals will run together, leading to a drop in blood pressure and loss of consciousness. Cholinergic urticaria is helped by antihistamines given regularly in severe cases or intermittently upon exposure to milder cases.
    The other form of heat urticaria is a very rare form in which welts develop within minutes at the site of locally applied heat, such as a hot water bottle or heating pad. Allergy does not appear to be a factor in this form of urticaria. Elimination of exposure to such items should control condition.


There are many patterns of hives with different underlying causes. In order to cope with urticaria, it is important to understand exactly which form of urticaria exists because the treatment is directly affected by the diagnosis. It is important to note that there are other skin conditions due to allergy, one of the most common being eczema or dermatitis. Moreover, allergic skin conditions are common and plague people the world over, but not all skin problems are allergic in origin. See a qualified medical physician for diagnosis and treatment.

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