Answer
- Type I Hypersensitivity reaction .
- treatment relieve the symptoms :
a- local cold compresses .
b- Antihistamines.
c- local & systemic corticosteroids.
Work Step by Step
Type I : Immediate ( Anaphylactic ) Hypersensitivity
- these reactions occur when an antigen ( allergen )
reacts with cell (= basophils & mast cells ) fixed
antibody ( IgE ) leading to degranulation of these cells
lesding to release of chemical mediators( include
Histamine, bradykinin, serotonin, prostaglandins,
esoinophil chemotactic factor of anaphylaxis ,
platelete activating factor PAF)
- these mediators cause vasodilatation & increased
premeability of capillaries as well as contraction of
smooth muscles & increased mucous secretion
causing the manifestations of the disease.
Insect Sting
- insect venom ( antigen )- antigen antibody reaction
in skin ( type I hypersensitivity )- degranulation
of mast cells - release of histamine & other
mediators - local vasodilatation & increased
capillary prmeability - allergic inflammation
( redness, hotness, pain (throbbing), swelling
(edema) , loss of function ).
- it may lead to Anaphylaxis which is the systemic
form of type I hypersensitivity reactions
it manifests by shock due to sudden decrease of
blood pressure, respiratory distress due to
bronchospasm ,cyanosis edema, urticaria etc.
shock may lead to death.
Treatment of Insect Sting
-designed to counteract the effect of released
chemical mediators or to block their actions.
- drugs used for treatment :
1- corticosterids.
2- antihistamines.
3- in systemic anaphylaxis : epinephrine is given
subcutaneously or intravenous.
