Urticaria
Urticaria is defined as transient pruritic swellings on the
skin.
It is also termed as wheals or hives.
Pathophysiology:
It occurs due to oedema in the superficial layers of the
skin.
Causes:
It can occur in association with:
Allergic reactions
Infection or
Physical stimuli
In association with vasculitis,pemphigoid or dermatitis
herpetiformis.
Angio-oedema is painful rather than itchy.
It appears as diffuse swelling that affects the deeper
layers of the skin.
It can occur rapidly and may involve the mucous membranes.
Urticaria is a fairly common skin disorder that may occur as
a single episode or recurrent.
The prognosis is varied and depends upon the underlying
cause.
Pathophysiology:
Urticaria results from release of histamine,bradykinin and
pro-inflammatory mediators being released from
basophils and mast cells in
response to various trigger factors.
These chemicals released by degranulation cause capillaries
and venules to leak causing tissue oedema.
Urticaria maybe IgE mediated with cross linking of two
adjacent IgE receptors or complement mediated causing direct degranulation of
mast cells or mast cells may directly be stimulated by an exogenous or
unknown
substance.
In patient with chronic urticarial, histamine canbe released
spontaneously or in response to non-specific
stimuli and their vasculature is
more sensitive to histamines.
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