Disulfiram acts by

DISULFIRAM is a DETERRANT which acts by blocking acetaldehyde dehydrogenase When acetaldehyde dehydrogenase is blocked there will be increased amount of acetaldehyde that acts on mast cells and results in release of histamine that in turn leads to allergic reaction. Thus when a patient on disulfiram takes alcohol there would be allergic reaction that prevents the patient from using the substance Ref.Kaplon and sadock, synopsis of psychiatry, 11 th edition, pg no. 624