Idiopathic urticaria

Hives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. They may also burn or sting. Often the patches of rash move around. Typically they last a few days and do not leave any long-lasting skin changes. Fewer than 5% of cases last for more than six weeks. The condition frequently recurs. Hives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. They may also burn or sting. Often the patches of rash move around. Typically they last a few days and do not leave any long-lasting skin changes. Fewer than 5% of cases last for more than six weeks. The condition frequently recurs. Hives frequently occur following an infection or as a result of an allergic reaction such as to medication, insect bites, or food. Psychological stress, cold temperature, or vibration may also be a trigger. In half of cases the cause remains unknown. Risk factors include having conditions such as hay fever or asthma. Diagnosis is typically based on the appearance. Patch testing may be useful to determine the allergy. Prevention is by avoiding whatever it is that causes the condition. Treatment is typically with antihistamines such as diphenhydramine and ranitidine. In severe cases, corticosteroids or leukotriene inhibitors may also be used. Keeping the environmental temperature cool is also useful. For cases that last more than six weeks immunosuppressants such as ciclosporin may be used. About 20% of people are affected. Cases of short duration occur equally in males and females while cases of long duration are more common in females. Cases of short duration are more common among children while cases of long duration are more common among those who are middle aged. Hives have been described at least since the time of Hippocrates. The term urticaria is from the Latin urtica meaning 'nettle'. Welts (raised areas surrounded by a red base) from hives can appear anywhere on the surface of the skin. Whether the trigger is allergic or not, a complex release of inflammatory mediators, including histamine from cutaneous mast cells, results in fluid leakage from superficial blood vessels. Welts may be pinpoint in size, or several inches in diameter. Angioedema is a related condition (also from allergic and nonallergic causes), though fluid leakage is from much deeper blood vessels in the subcutaneous or submucosal layers. Individual hives that are painful, last more than 24 hours, or leave a bruise as they heal are more likely to be a more serious condition called urticarial vasculitis. Hives caused by stroking the skin (often linear in appearance) are due to a benign condition called dermatographic urticaria. Hives can also be classified by the purported causative agent. Many different substances in the environment may cause hives, including medications, food and physical agents. In perhaps more than 50% of people with chronic hives of unknown cause, it is due to an autoimmune reaction. Drugs that have caused allergic reactions evidenced as hives include codeine, sulphate of morphia, dextroamphetamine, aspirin, ibuprofen, penicillin, clotrimazole, trichazole, sulfonamides, anticonvulsants, cefaclor, piracetam, vaccines, and antidiabetic drugs. The antidiabetic sulphonylurea glimepiride, in particular, has been documented to induce allergic reactions manifesting as hives. Drug-induced hives has been known to have an effect on severe cardiorespiratory failure. The most common food allergies in adults are shellfish and nuts. The most common food allergies in children are shellfish, nuts, eggs, wheat, and soy. One study showed Balsam of Peru, which is in many processed foods, to be the most common cause of immediate contact urticaria. A less common cause is exposure to certain bacteria, such as Streptococcus species or possibly Helicobacter pylori.