Urticaria

Urticaria is a skin reaction that produces raised, itchy wheals, often changing shape or location over hours. It results from temporary fluid leakage into the skin.

Mast cell: A tissue immune cell that releases histamine and other inflammatory mediators. Mast-cell mediator release drives the skin changes in most urticaria.
Chronic spontaneous urticaria: Urticaria with recurrent wheals, angioedema, or both for more than six weeks without a consistent external trigger. This is the principal chronic form when episodes arise without an identifiable inducible cause.
Second-generation antihistamine: A newer H1-receptor blocker designed to relieve allergy symptoms with less sedation than older antihistamines. These medicines are the usual first-line treatment for urticaria symptoms.
Atopic dermatitis: A chronic inflammatory skin disease marked by itchy, dry, eczematous lesions. Its persistent eczematous patches differ from transient urticarial wheals.
Histamine: A signaling molecule that can widen blood vessels, increase vascular permeability, and stimulate sensory nerves. Histamine produces much of the itching and fluid leakage in wheals.
Chronic inducible urticaria: Urticaria repeatedly triggered by a reproducible physical or environmental stimulus. Its predictable triggers distinguish it from spontaneous chronic episodes.
Omalizumab: A monoclonal antibody that binds free immunoglobulin E and is used for selected allergic diseases. It can control chronic spontaneous urticaria that remains active despite antihistamines.
Contact dermatitis: Skin inflammation caused by direct exposure to an irritant or allergen. Its exposure-shaped rash usually persists longer than individual urticaria wheals.
Wheal: A transient, raised area of skin swelling caused by fluid accumulating in the superficial dermis. A wheal is the defining visible lesion of urticaria.
Acute urticaria: Urticaria lasting six weeks or less, often arising during an infection or after an exposure. The acute-versus-chronic distinction is based on how long episodes recur.

Linked from 19 pages