An in vitro method for diagnosing a contact allergy in a subject comprises: (i) providing (a) a contact allergen; (b) T-cells from said subject; and (c) a surface to which is immobilized a first specific binding agent capable of specifically binding to a cytokine released from a T-cell in response to said allergen; (ii) contacting said sample with said allergen under conditions which are suitable for (a) release of said cytokine by T cells that have been presensitized in vivo to said allergen; and (b) binding of said cytokine to said first specific binding agent; and (iii) detecting binding of said substance to said first specific binding agent. A kit which enables the method to be carried out is also described.