Wheals arise on the skin similar to that caused by sting of a nettle. Dilatation of capillaries accompanied by increased permeability of their walls so the serum leaks out and accumulates in the corium. Wheals first appear red, later pale because of compression of capillaries by serum. Vascular reactions are caused by: (a) Histamine and histamine like substance. (b) Certain toxins and venoms. (c) Certain drugs. (d) Physical factors. Allergic urticaria: The substances which cause allergic urticaria enter the body by way of the following: Ingestion, inhalation, injection, or local application. Treatment: Suppressive: Chlorpheniramine—Adrenaline 0.5 to 1 ml subcutaneously once or twice daily. Corticosteroids oral/parenteral in nonresponsive cases. In resistant cases, combination of H1 and H2 blocked. Immunotherapy with histaglobulin in selected cases. Papular urticaria: Occurs in childhood. Eruption usually in the evening 1 to 2 cm in diameter. Angio-oedema (giant urticaria): Rapid swelling of skin subcutaneous tissue is involved. Eruption consists of diffuse or circumscribed. Swelling 2.5 to 7.5 cm. Types: Congenital (AD), allergic, recurs indefinitely. Diagnosis is based on clinical picture. Treatment for angio-oedema: Congenital (inhibited type) which is due to C1 esterase inhibitor deficiency/dysfunctions may require transfusion of C1 esterase inhibitor. Acquired type: Corticosteroid, epinephrine, antihistamines.