Abstract: 【Abstract】 Allergic contact dermatitis （ACD） is a T cell-mediated inflammatory skin disease induced by contact allergens. The role of mast cells in ACD remains controversial. In the sensitization phase, mast cells play a pro-inflammatory role by releasing inflammatory cytokines to promote recruitment of neutrophils, and affect the sensitization process by stimulating or inhibiting the migration of dendritic cells. During the elicitation phase, mast cells promote non-allergen-specific inflammation, and enhance allergen-specific inflammation in moderate ACD, but inhibit allergen-specific inflammation in severe and chronic ACD. In addition to the IgE-Fcε receptor I-histamine pathway, Mas-related G-protein coupled receptor B2/X2 （MrgprB2/X2） can mediate the activation of mast cells, leading to the release of tryptase to drive non-histaminergic itch, and may serve as a new target for the treatment of ACD.

Key words: Dermatitis, allergic contact, Mast cells, Allergens, Sensitization