Hives is a skin disease. It refers to a condition when red welts appear on the surface of the skin. These welts are often itchy and can be raised such that they will appear like bumps. Hives is also known as Urticaria in medical circles. Though Hives can be caused by non allergic causes, more often than not the causes of hives are allergic in nature. Indeed, hives that last for a short duration of time, usually less than five or so weeks is caused by allergic reactions and is simply referred to as acute hives or acute urticaria. On the contrary, chronic hives or chrionic urticaria usually lasts a longer period usually more than six weeks and are less likely to have been caused by allergic reactions.
Some of the causes of urticaria that are rarely experienced are pressure, induced friction, extreme temperature changes, sunlight and sometimes even exercise. Indeed, most cases of chronic urticaria have unknown causes. We refer to them as idiopathic causes, with most of the patients being autoimmune. When the chronic form of hive is as a result of viral infection, then we refer to it as viral exanthema.
Hives is often classified depending on its magnitude and cause. Apart from the acute and chronic hive, we have the drug induced type of hives, physical hives, hives caused by pressure or delayed pressure, cholinergic or stress induced hives, exercise induced hives or anaphylaxis and vibratory angioderma among many others. The drug induced type of hive is caused by allergic reactions from consuming drugs such as penicillin, anti-convulsants, aspirin, sulfonamides and suphonylurea among other anti diabetic medicines. Physican hives is caused by aggressive stroking of the skin, more commonly in medical terms as Dermotograhism. Luckily, the welts that appear on the skin due to physical abrasion usually disappear within one hour or so, even as quick as thirty minutes.