What is the main cell behind the pathophysiology of contact dermatitis?

• A. Mast cell
• B. B cell
• C. NK cell
• D. T cell

Answer: (D)

Contact dermatitis is a delayed-type hypersensitivity reaction in the skin driven primarily by T lymphocytes. A hapten from the allergen binds skin proteins, and Langerhans cells present this hapten-protein complex to T cells in regional lymph nodes, initiating sensitization and memory formation. Upon re-exposure, these memory T cells recognize the hapten and release cytokines that recruit and activate macrophages and other inflammatory cells, producing the classic eczema-like rash with redness, swelling, and vesicles over 24 to 72 hours. While other immune cells have roles in different reactions, they are not the main drivers here. Therefore, T cells are the key players in the pathophysiology of contact dermatitis.