Delay in the development of the allergic response to metals following intratracheal instillation.

Intracheal intubation with the soluble metal salts potassium dichromate (K2Cr2O7) and nickel sulphate (NiSO4) causes a delay of up to 8 weeks in the development of delayed hypersensitivity to the specific agent. It is suggested that absorption of sensitizers by the respiratory route may, under certain circumstances, induce a state of specific immunological unresponsiveness, rather than necessarily lead to the development of a state of allergic sensitivity.