Hives, also known as urticaria, affect about 20 percent of people at some point during their lifetime. Hives often start as itching, followed by swollen, red welts. The itching may be mild to severe. Scratching, alcoholic beverages, exercise, and emotional stress may worsen the symptoms. There are two categories of hives: “acute hives” and “chronic hives”.
- Acute hives are ones that last six weeks or less and are generally caused by any of the following:
- Medications, such as aspirin and antibiotics
- Foods or food additives, particularly peanuts or other nuts, shellfish and eggs
- Insect bites or stings
- Blood transfusions
- Infections, including strep throat, urinary tract infections, mononucleosis, hepatitis and the common cold
Chronic urticaria is hives that last or recur for more than six weeks. In many cases, the cause of chronic hives is difficult to determine. The immune system is the cause of about 50 percent of hives cases where an external cause has not been otherwise identified.