If you are exposed to an allergen or chemical irritant, your skin may develop itchy, red, raised welts on the skin called hives. Often hives spread or blend together to form larger areas of raised lesions. Harmless and non-contagious, hives generally clear up on their own.
Hives develop when mast cells release histamine and other chemicals into your bloodstream, causing small blood vessels to leak. Generally, hives are an allergic reaction to a food, animal or medication. Sun exposure, stress, excessive perspiration and other more serious conditions, like lupus, can bring on hives.
Individual hives can take from 30 minutes to 36 hours to disappear. Chronic hives, referred to as urticaria, last longer than six weeks to go away, but frequently reoccur. If swelling occurs below the surface of the skin, a condition called angioedema, you should seek medical attention because angioedema can affect the internal organs.
Signs of hives include:
- Developing in batches
- Often raised
- Small, round rings or large patches with a red flare
- Usually itch
Usually, hives develop suddenly and disappear almost as quickly with no treatment. You can use over-the-counter creams and antihistamines to control itching if it becomes a problem. For cases of chronic hives, your physician may prescribe antihistamines or oral corticosteroids. The best prevention for hives is avoidance of any known triggers, such as certain foods, stress or extreme changes in weather.