Urticaria results from which type of hypersensitivity reaction?

Urticaria results from which type of hypersensitivity reaction?

• A. Type 1
• B. Type 2
• C. Type 3
• D. Type 4

Answer: (A)

Urticaria is an immediate, IgE-mediated allergic reaction. An allergen cross-links IgE antibodies bound to receptors on mast cells and basophils, triggering rapid degranulation and release of histamine and other mediators. Histamine then increases vascular permeability and causes the superficial dermal edema that forms the itchy wheals of hives. This rapid, IgE-driven process defines a Type I hypersensitivity reaction. In contrast, Type II involves antibodies directed at cell surfaces, Type III involves immune complex deposition, and Type IV is T-cell–mediated delayed-type hypersensitivity, none of which are the primary mechanism of urticaria.

Urticaria is an immediate, IgE-mediated allergic reaction. An allergen cross-links IgE antibodies bound to receptors on mast cells and basophils, triggering rapid degranulation and release of histamine and other mediators. Histamine then increases vascular permeability and causes the superficial dermal edema that forms the itchy wheals of hives. This rapid, IgE-driven process defines a Type I hypersensitivity reaction. In contrast, Type II involves antibodies directed at cell surfaces, Type III involves immune complex deposition, and Type IV is T-cell–mediated delayed-type hypersensitivity, none of which are the primary mechanism of urticaria.