Hives




Hives - also known as urticaria - are raised, red, itchy welts (wheals) of various sizes that appear and disappear on your skin. Angioedema, a similar swelling, causes large welts deeper in your skin, especially near your eyes and lips. A more serious condition - hereditary angioedema (HAE) - is an uncommon, inherited disorder, which can cause sudden, severe and rapid swelling of your face, arms, legs, hands, feet, genitalia, digestive tract and airway. As many as one in five people experiences acute hives or angioedema at one time or another. HAE, on the other hand is rare.

In most cases, hives and angioedema are harmless and don't leave any lasting marks, even without treatment. The most common treatment for hives and angioedema is antihistamine medications. Serious angioedema can be life-threatening if swelling causes your throat or tongue to block your airway and leads to loss of consciousness.

Signs and Symptoms

Hives can be either acute or chronic. By definition, acute hives can last from less than a day to up to six weeks, whereas chronic hives last more than six weeks - sometimes occurring for months to years at a time. Angioedema and hives can occur at the same time. Hives are raised, red bumps of various sizes that appear and disappear on your skin. They're often may look similar to mosquito bites and cause itchy skin. Hives tend to occur in batches. Angioedema is similar to hives but occurs deeper in the skin. Signs and symptoms of angioedema include large welts or swelling of the skin that may occur in the following locations:
  • Especially near your eyes and lips
  • On your hands
  • On your feet
  • On your genitalia
  • Inside your throat
Signs and symptoms of hereditary angioedema include:
  • Sudden and severe swelling of your face, arms, legs, hands, feet, genitalia, digestive tract and airway
  • Abdominal cramping as a result of digestive tract swelling
  • Difficulty or obstructed breathing due to swelling of your airway
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Causes

The lesions of hives and angioedema are caused by inflammation in the skin. In some cases, hives and angioedema are triggered when certain cells (mast cells) release histamine and other chemicals into your bloodstream and skin.

Allergic reactions to medications or foods can cause acute hives or angioedema. Many allergens have been identified. Examples include:
  • Foods. Many foods can cause problems in sensitive people, but shellfish, fish, nuts, eggs and milk are frequent offenders.
  • Medications. Almost any medication may cause hives or angioedema; common culprits include antibiotics, aspirin, ibuprofen (Advil, Motrin, others) and blood pressure medications.
  • Other allergens. Other substances that can cause hives and angioedema include direct contact with pollen, animal dander, latex and insect stings.
Additional triggers that may produce hives or angioedema include:
  • Physical factors. Environmental factors also can result in the release of histamine with subsequent hives or angioedema in some people. Examples of these factors include heat, cold, sunlight, water, pressure on the skin, emotional stress and exercise.
  • Dermatographism. The name of this condition literally means "write on the skin." When pressure is applied to the skin or the skin is scratched, raised lines appear on those areas due to histamine-based angioedema that leads to swelling beneath the skin.
In addition to these triggers, hives and angioedema sometimes may occur in response to your body's production of antibodies. Some examples of situations in which this might occur include blood transfusions; immune system disorders, such as lupus or cancer; certain thyroid disorders; and infections, such as hepatitis, or even a cold.

Hereditary angioedema is an inherited form of angioedema and is related to low levels or abnormal functioning of certain blood proteins (C1 inhibitors). These inhibitors play a role in regulating how your immune system functions.

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Risk Factors

You may be at greater risk of hives and angioedema if you:
  • Have had hives or angioedema before
  • Have had other allergic reactions
  • Have a disorder associated with hives and angioedema, such as lupus, lymphoma or thyroid disease
  • Have a family history of hives, angioedema or hereditary angioedema
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Screening and Diagnosis

It's sometimes impossible to determine the cause of hives or angioedema. Your doctor will begin by asking you about your medical history. This may include asking you to create a detailed diary of exposure to possible irritants. It's important to tell your doctor about all medications you take, including over-the-counter (OTC) drugs and herbal remedies, even if you don't take them every day. Your doctor may also want to conduct allergy tests, such as skin tests.

If your doctor suspects HAE, he or she may ask for blood tests to check for levels and function of specific blood proteins. If your doctor suspects allergy to food, latex, animal dander, pollen or medication, he or she may recommend allergy skin or blood tests.

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Treatment

If your symptoms are mild, you may not need treatment. The standard treatment for hives and angioedema is antihistamines, which block the symptom-producing release of histamine. These include:

Nonprescription medications
  • Diphenhydramine (Benadryl, others)
  • Chlorpheniramine (Chlor-Trimeton, others)
  • Clemastine (Tavist, others)
  • Loratadine (Alavert, Claritin)
Antihistamines such as diphenhydramine, chlorpheniramine and clemastine may cause drowsiness. Loratadine usually doesn't cause drowsiness.

Prescription medications
  • Desloratadine (Clarinex)
  • Fexofenadine (Allegra)
  • Cetirizine (Zyrtec)
  • Hydroxyzine (Atarax, Vistaril)
Occasionally for severe hives or angioedema, doctors may prescribe an oral corticosteroid drug - such as prednisone - which can help lessen swelling, redness and itching.

Treatment for HAE
Although useful in treating hives and angioedema, these medications are often ineffective in treating hereditary angioedema. Medications used specifically to treat HAE on a long-term basis include certain androgens, such as danazol (Danocrine), that help regulate levels of blood proteins. Additionally, clinical trials testing new medications to treat HAE are ongoing.

Emergency situations
For a severe attack of hives or angioedema, you may need an emergency injection of adrenaline (epinephrine) and a trip to the emergency room. If you have repeated attacks, despite treatment, your doctor may prescribe - and instruct you how to use - adrenaline to carry with you for use in emergency situations.

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Prevention

To lower your likelihood of experiencing hives or angioedema, take the following precautions:
  • Avoid known triggers. These may include certain foods or medications, or situations, such as temperature extremes, that have triggered past allergic attacks.
  • Keep a diary. If you suspect foods of causing the problem, keep a food diary. Be aware that some foods may contain ingredients that are listed by less common names on the label.
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Information obtained from National Institute of Health
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