The below rash was seen in a person. He has a family history of asthma. What could be the most probable diagnosis?
High-Yield Explanation
Ref. Rook's Textbook of Dermatology, Pg 99
Allergic contact dermatitis is a form of dermatitis/eczema caused by an allergic reaction to a material, called an allergen, in contact with the skin.
Pathogenesis
Allergic contact dermatitis is a type 4 or delayed hypersensitivity reaction and occurs 48–72 hours after exposure to the allergen.
The mechanism involves CD4+ T-lymphocytes, which recognise an antigen on the skin surface, releasing cytokines that activate the immune system and cause the dermatitis.