Contact dermatitis is what type of hypersensitivity reaction?

Contact dermatitis is what type of hypersensitivity reaction?

• A. Type 1
• B. Type 2
• C. Type 4
• D. Type 3

Answer: (C)

Allergic contact dermatitis is a delayed-type hypersensitivity reaction driven by T cells rather than antibodies. When a skin allergen acts as a hapten and binds to skin proteins, Langerhans cells present this complex to T cells, which become sensitized. On re-exposure, these memory T cells release cytokines that recruit macrophages and other inflammatory cells, leading to the dermatitis that typically appears 24–72 hours after contact. This cell-mediated, delayed response distinguishes it from immediate IgE-mediated reactions (Type 1), antibody-dependent cytotoxicity (Type 2), and immune complex–mediated reactions (Type 3). Hence, contact dermatitis is Type 4.

Allergic contact dermatitis is a delayed-type hypersensitivity reaction driven by T cells rather than antibodies. When a skin allergen acts as a hapten and binds to skin proteins, Langerhans cells present this complex to T cells, which become sensitized. On re-exposure, these memory T cells release cytokines that recruit macrophages and other inflammatory cells, leading to the dermatitis that typically appears 24–72 hours after contact. This cell-mediated, delayed response distinguishes it from immediate IgE-mediated reactions (Type 1), antibody-dependent cytotoxicity (Type 2), and immune complex–mediated reactions (Type 3). Hence, contact dermatitis is Type 4.