Definition Hives are red, itchy welts on the skin that come and go over the course of minutes or hours. All types of hives can cause itching. They usually form on the skin but sometimes hives form in the soft tissue of the mouth, eyes and throat.
What is going on in the body? Hives are the result of an allergic reaction in the skin. They are caused by the release of histamine. Histamine is released when a person's immune system tries to fight a foreign substance. The release of histamine causes inflammation in the skin.
What are the signs and symptoms of the condition? Hives are characterised by itchy red welts and swelling of facial features. Hives can cause a reaction that involves the whole body, not just the skin. This is called anaphylaxis.
What are the causes and risks of the condition? There are several known factors that cause histamines to be released, and hives to form. These include:
underlying systemic disease such as asthma, a condition that causes inflammation and obstruction of the airways in the lungs
blood products given intravenously, or into the vein
scratching
heat or cold
exposure to sunlight
pressure
Anaphylaxis is a medical emergency that can cause difficulty breathing and lead to death. It is important to call 000 immediately if anaphylaxis is suspected.
What can be done to prevent the condition? Antihistamine medications, such as promethazine, diphenhydramine, cetirizine or loratadine, can be used to prevent hives. An individual should also avoid the substance that provoked the reaction if it is known. Adrenaline is used to treat severe reactions such as anaphylaxis.
How is the condition diagnosed? A doctor can diagnose hives after examining the affected person and listening to an account of the event.
What are the long-term effects of the condition? Hives cause:
discomfort
skin irritation and breakdown
skin infection
What are the risks to others? Hives are not contagious.
What are the treatments for the condition? Hives can be treated in the following ways:
identifying and removing the substance that provoked the outbreak
using oral antihistamines such as promethazine, diphenhydramine, cetirizine or loratadine
using oral corticosteroids such as prednisone
giving Adrenaline for anaphylaxis
What are the side effects of the treatments? Both oral antihistamines and oral corticosteroids can have side effects, such as drowsiness, dry mouth, constipation and the inability to urinate. Antihistamines, especially the older ones such as diphenhydramine, can cause more severe reactions in the elderly.
What happens after treatment for the condition? Hives generally clear up without any long term problems. It is important to identify the cause, however, and treat any underlying conditions.
How is the condition monitored? If hives occur frequently, a doctor should be consulted.
Author: Lynn West, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 18/09/2004 Contributors Potential conflict of interest information for reviewers available on request
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