Allergic Contact Dermatitis
The characteristics of allergic dermatitis are as follows:
Past history of exposure to an allergen
A time period of 48 to 96 hours between exposure to allergen
and clinical manifestation of allergy.
Manifestation of allergy in previously exposed areas even if
allergen contact occurs at a distant site.
Clinical features of allergy persisiting for number of
years.
Pictures of allergic contact dermatitis
Pathophysiology:
Allergic contact Dermatitis is a result of type IV hypersensitivity
reaction (which is a type of delayed hypersensitivity)
Antigens enter the epidermis and get combined by a protein
mediator which are engulfed by Langerhans cells.
T lymphocytes in regional lymph nodes become sensitized to
the antigen.
On future exposure to antigen,an allergic reaction occurs
due to accumulation of sensitized T lymphocytes at site of inflammatory
response.
Irritant Contact Dermatitis:
This maybe caused by chemicals or physical factors.
Causative Chemicals include:
Detergents
Cosmetic products
Physical factors include:
Clothing materials
Repetitive mechanical trauma
Past exposure is not required for its manifestation.
No comments:
Post a Comment