Allergies: Hives (Urticaria)
PATIENT EDUCATION SERIES
What are hives? Expected Course
The body’s immune system is designed to produce More than 10% of people get hives. The hives gener-
various factors to fight foreign substances, includ- ally come and go for 3 to 4 days and then mysteri-
ing bacteria and viruses that the immune system ously disappear.
perceives as threatening. An allergic response
occurs when the body’s immune system over-re- Home Treatment
sponds, or is hypersensitive to particles known as Antihistamine medication: The best drug for wide-
allergens. Common allergens include plant pollens, spread hives is an antihistamine. It may not cure
molds, dust mites, animal dander, industrial chemi- the hives, but it will reduce their number and re-
cals, food, medicines and insect venom. lieve itching. Diphenhydramine (Benadryl) is avail-
able without a prescription. It comes in both liquid
Important components of the immune system are and tablet form. Diphenhydramine may cause
the antibodies produced by lymph tissue. A key drowsiness, so do not drive while taking it. Contin-
player in the allergic response is the antibody ue taking your antihistamine for a day or two after
known as immunoglobulin E (IgE). IgE is overpro- the hives disappear to be sure they are completely
duced in certain people, usually those with inher- gone. Your medical provider can prescribe a non-
ited susceptibility. sedating antihistamine if necessary.
During an allergic attack, these antibodies attach Avoidance: Avoid anything you think may have
to cells known as mast cells, which are generally caused the hives. If you have recently started a
concentrated in the lungs, skin and mucous mem- new medication, discontinue it if possible, until you
branes. Once IgE binds to mast cells, these cells have called Health Services for advice. For hives
are programmed to release a number of chemicals. triggered by pollen or animal contact, take a cool
One of these chemicals, histamine, opens the blood shower or bath. Hot showers, vigorous toweling,
vessels and causes skin redness and swollen mem- exercise, tight clothing or any other factors that
branes. Histamine causes many of the symptoms stimulate or inflame your skin may make symptoms
associated with allergies. Hives are a common al- worse. For localized hives, wash the allergic sub-
lergic reaction involving the skin. stance off the skin with soap and water. Localized
hives usually disappear in a few hours so Benadryl
What causes hives? is often not needed.
Widespread hives are an allergic reaction to food,
medicine, viral infection, insect bite or environmen-
tal exposures. Often the cause cannot be deter-
Seek Emergency Care Immediately If:
mined. Hives localized to just one part of the body Breathing or swallowing becomes difficult
are usually due to skin contact with plants, pollen, or you start feeling ill.
food or pet saliva. Hives are not contagious.
Call Health Services during regular hours
Symptoms include: or come in to see a provider if:
♦ Very itchy rash ♦ Symptoms are worse, or if most of the itch is not
♦ Raised pink lesions with pale centers, ranging in relieved after you have been taking an
size from ½ inch to several inches wide. antihistamine for 24 hours.
♦ Variable shapes ♦ The hives last for more than one week.
♦ Rapid and repeated change in location, size and ♦ You have other concerns or questions.
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