the skin eruptions are erythematous, raised above the skin level, with intense
itching and usually worsened by itching & with slight local warmth.
These eruptions can remain on the body for variable period, anywhere
between few seconds to even hours. They have tendency to disappear and
reappear. They tend to disappear without leaving behind any trace.
Location and duration:
Well, urticaria may appear on any part of the skin.
Angioedema is a condition when deep tissues are affected.
The typical lesions may last for one minute to half an hour.
Some may last even longer. Some patients may get the
eruptions once in a while and some may have many times
during the day. It may be restricted to a couple of spots in
some patients, while some may have wide spread rashes
appearing for days or even months together.
There are acute, subacute, chronic and recurring variants as
far as the frequency and duration are concerned.
Under the microscope, a typical urticarial rash may
exhibit perivascular, cellular infiltrate consisting of
lymphocytes and eosinophils, is indicative of its allergic
behavior. There are findings related to oedema (swelling)
and mucosal inflammation.
The Inner War:
The urticaria rash is a symptom of an allergic and
immunological event taking place at the dermal level. The
exact understanding is illusive to an extent. In brief,
urticaria is a hypersensitive reaction due to the histamine
release. The histamine release could be from the mast cells
when antigens and antibodies (IgM or IgG) combine to
activate the immunological reaction. The histamine release
could IgE induced. There are certain drugs, pharmacological
agents (e.g.: antibiotics, morphine, aspirin, etc.), food
articles (proteins, milk products, etc.) Urticaria is a sign
of antigen-antibody reaction.
During this process of antibody-antigen reaction, histamine
and/or acetyl choline is generated which has the property of
causing vessel dilatation (vasodilation) swelling, itching,
pain and rash.