Urticaria is the medical term used to denote hives, which are characterized by dark red, itchy bumps. Such raised bumps with red borders can develop anywhere on the skin, and are commonly referred to as 'wheals'. Usually, hives develop as allergic reactions. The condition may also be linked to other causative factors. In some cases, hives last for more than six weeks, and this condition is termed chronic urticaria, which is usually, not caused by allergies.