Hives

What are hives?
The body's immune system is designed to produce various factors to fight foreign substances, including bacteria and viruses that the immune system perceives as threatening. An allergic response occurs when the body's immune system over-responds, or is hypersensitive to particles known as allergens. Common allergens include plant pollens, molds, dust mites, animal dander, industrial chemicals, food, medicines and insect venom. More than 10% of people get hives.

Important components of the immune system are the antibodies produced by lymph tissue. A key player in the allergic response is the antibody known as immunoglobulin E (IgE). IgE is overproduced in certain people, usually those with inherited susceptibility.

During an allergic attack, these antibodies attach to cells known as mast cells, which are generally concentrated in the lungs, skin and mucous membranes. Once IgE binds to mast cells, these cells are programmed to release a number of chemicals. One of these chemicals, histamine, opens the blood vessels and causes skin redness and swollen membranes. Histamine causes many of the symptoms associated with allergies. Hives are a common allergic reaction involving the skin.

What causes hives?
Widespread hives are an allergic reaction to food, medicine, viral infection, insect bite or environmental exposures. Often the cause cannot be determined. Hives localized to just one part of the body are usually due to skin contact with plants, pollen, food or pet saliva. Hives are not contagious.

What are the symptoms?
Common symptoms of hives include:

• Very itchy rash
  
• Raised pink lesions with pale centers, ranging in size from ½ inch to several inches wide
  
• Variable shapes
  
• Rapid and repeated change in location, size and shape

Seek emergency care immediately if breathing or swallowing becomes difficult or you start feeling ill.

How long do symptoms last?
The hives generally come and go for 3 to 4 days and then mysteriously disappear.

Call Health Services at 401.863-3953 during regular hours or come in to see a medical provider if:

• Symptoms are worse
  
• If most of the itch is not relieved after you have been taking an antihistamine for 24 hours.
  
• The hives last for more than 1 week.
  
• You have other concerns or questions.

How are they treated?
The best drug for widespread hives is an antihistamine. It may not cure the hives, but it will reduce their number and relieve itching. Benadryl or its generic equivalent is available without a prescription. It comes in both liquid and tablet form. Benadryl may cause drowsiness, so do not drive while taking it. Continue taking your antihistamine for a day or 2 until you are sure the hives are completely gone. Your medical provider can prescribe a non-sedating antihistamine if necessary.

Can hives be prevented?
Avoid anything you think may have caused the hives. If you have recently started a new medication, discontinue it if possible, until you have called Health Services at 401.863-3953 for advice. For hives triggered by pollen or animal contact, take a cool shower or bath. Hot showers, vigorous toweling, exercise, tight clothing or any other factors that stimulate or inflame your skin may make symptoms worse. For localized hives, wash the allergic substance off the skin with soap and water. Localized hives usually disappear in a few hours so Benadryl is often not needed.

Links you can use
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last modified: March 19, 2009