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 also in the soft tissues of the mouth, eyes and throat.
What is going on in the body?
In an allergic reaction, a person's immune system has been "primed", or "sensitized" to any one of a number of foods, medications, or other substances from the environment. In response to the substance, the immune cells release a chemical known as histamine. Histamine, in turn, acts on the capillaries in the skin, causing them to dilate and leak fluids. These fluids collect under the skin in welts which we recognize as hives.
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
- 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
- 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 for emergency medical assistance immediately if anaphylaxis is suspected.
What can be done to prevent the condition?
Antihistamine medications, such as diphenhydramine (i.e., Benadryl), cetirizine (i.e., Zyrtec) or loratadine (i.e., Alavert, Claritin), 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 professional can diagnose hives after examining the affected person and listening to an account of the event.
Long Term Effects
What are the long-term effects of the condition?
- 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 diphenhydramine, cetirizine
- using oral corticosteroids such as prednisone
- giving epinephrine
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. However, it is important to identify the cause and treat any underlying conditions.
How is the condition monitored?
If hives occur frequently, a healthcare professional should be consulted.