Hives are an inflammation of the skin triggered when the immune system releases histamine. This causes small blood vessels to leak, which leads to swelling in the skin.
Swelling in deep layers of the skin is called angioedema. There are two kinds of urticaria, acute and chronic. Acute urticaria may occur after eating a particular food, medication or coming in contact with a particular trigger. It can also be triggered by non-allergic causes such as heat or exercise, as well as medications, foods or insect bites. Acute urticaria is classified when the hives occur less than 6 weeks. Chronic urticaria can last for many months or years. Although they are often uncomfortable and sometimes painful, hives are not contagious. Depending on whether you have acute or chronic urticaria, your allergist will determine the most appropriate tests to perform. There are many medications used to treat these symptoms, but the pros and cons of each one need to be discussed with your allergy specialist. If you are having hives call your doctor immediately and he/she may refer you to an allergy doctor to determine the cause of them. If you feel your throat is closing and/or have difficulty breathing call 911 or go immediately to your nearest emergency room.
For treatment of chronic hives, please see our blog post, http://allergylosangeles.com/allergy-blog/stepwise-approach-to-chronic-urticaria/