Hives can be caused by many things, including illnesses, infections, allergic reactions, or contact with irritating substances. In rare cases, hives can be caused by stress, infection, or illness. In most cases, however, hives are caused by an allergic reaction to a medication, food, or an environmental irritant, like an allergen. When the body encounters something it’s allergic to, it releases substances known as histamines into the blood. Histamines are chemicals the body produces to fight off infections and intrusive substances, and they work by creating swelling and itching – two of the symptoms associated with hives.
Fortunately, most hives are acute and easily alleviated by taking OTC allergy medications. Most hives clear up within 24 hours. As existing hives clear up, though, new ones can form. And when they do, they can develop in the same or different areas of the skin, creating an uncomfortable experience for the person suffering from hives. For most people, the formation of new hives can persist for a few days or weeks. If new hives appear for six weeks or longer, you will likely meet the diagnostic criteria for a condition known as chronic hives.
