In acute urticaria, usually the underlying cause of the disease is easily identified. According to the modern view, an urticarial reaction can be explained as the release of histamine and possibly other vasoactive mediators which suddenly increase the vascular capillary permeability, thus allowing the escape of fluid from circulation into the tissues. This may happen in response to a number of stimuli which can be of physical, chemical, pharmacological and immunological origin. Most of the times patients of chronic urticaria are at a loss to find any particular reason for their problem.

If we look more closely at the etiology of acute urticaria, anything on earth which acts against a particular physiological idiosyncrasy of a person can precipitate an attack. Of the dietary reasons, an unsuitable food item or its incompatible combination, including chemical preservatives or additives, are the most identifiable causes of acute urticaria. Many drugs such as antibiotics and painkillers, inhalants like grass pollens, house dust, scents and deodorants, parasitic infestations like roundworm infection and insect stings, environmental aberrations and sudden exposure to hot and cold weather and transfusion reactions can instantly produce an attack of urticaria.