Hives are a form of skin rash caused by an allergic reaction. They typically present as a red, itching rash which is raised above the level of normal skin. Hives can affect the skin anywhere on the body and are commonly seen on the face, lips, head, hands, and feet. Hives are known medically as urticaria.
Hives cause a very distinctive rash. The rash is typically a series of small raised bumps on the skin which are very itchy. Smaller hive lesions will join together to form large plaques. Oftentimes the individual hives and plaques will change shape and size over a period of minutes or hours. This rapid change in shape and size is very specific to hives.
Hives are most commonly caused by an allergic hypersensitivity reaction, although in many cases these specific cause of this hypersensitivity is not identified. Hypersensitivity reactions are regulated by a hormone known as histamine. Histamine is released by cells in your immune system in response to allergens in the environment. These histamines cause localized rash and swelling in the tissues where they are released. This rash and swelling are known as hives.
Release of histamine, and the resulting hive rash, can be caused by a variety of triggers which activate your immune system. Insect bites or exposure to animals or animal fur are common causes. Many foods can cause a hypersensitivity. Some common foods involved in allergic reactions include shellfish, peanuts, and eggs, although there can be many others.
Infections of various kinds can induce a hypersensitivity reaction and histamine release leading to hives.
Many medications that people are allergic to can induce hives. This is commonly seen in people who are allergic to aspirin and some antibiotics such as penicillin.
There is an almost limitless number of other causes of hypersensitivity reactions. People can be allergic to a wide range of chemicals found in their environment, any one of which can cause a hypersensitivity and hive-like rash.
The best way to prevent hives is to identify the source which is causing the allergic reaction. Once you have identified the source, avoidance is the best prevention.
People who have severe hypersensitivity to a known allergen often will carry medication with them to control hives should they break out. This is not done routinely, but only by people who have extremely severe reactions.
Antihistamines are used to control hives. They act by reducing the amount of histamine released by your immune system during an allergic response. Claritin and Benadryl are commonly used antihistamines. Epinephrine injections are used to control severe reactions.
If you break out in a rash which you suspect may be hives, make an appointment to see your doctor. There are allergy skin tests which can be done to determine specific allergens which may have triggered the reaction. If you have recently started taking a new medication, call your doctor and inform them of the rash immediately. If the hives form in an area of the mouth or lips which prevent a person from breathing easily, contact your local emergency services immediately.
