Hives are red, very itchy, swollen areas of the skin. Hives arise suddenly and may leave quickly in 1-2 hours or can last as long as 48 hours. They often appear in clusters, with new clusters appearing as other areas clear.
Physicians refer to hives as urticaria.
Over one-fifth of the population has suffered an eruption of hives at some point in their lives. Hives can be caused by allergic or non-allergic mechanisms. In a majority of chronic cases, the exact cause is unknown. Often hives are caused by an adverse reaction to some food or drug. Foods likely to cause hives include chocolate, nuts, tomatoes, shellfish, and berries.