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.

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:

	Allergy to medications or substances in the environment
	Acute or chronic infections
	Foods
	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

Anaphylaxis is a medical emergency that can cause difficulty breathing and lead to death. It is important to call 999 immediately if anaphylaxis is suspected.

What can be done to prevent the condition?
Antihistamine medications, such as diphenhydramine, satirising or loratadine, can be used to prevent hives. An individual should also avoid the substance that provoked the reaction if it is known. Epinephrine is used to treat severe reactions such as anaphylaxis.

How is the condition diagnosed?
A healthcare provider 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?

	Discomfort
	Skin irritation and breakdown
	Skin infection

What are the risks to others?
Hives are not contagious.

For information about treatments for allergies, click here