Chloramine T, an organic, highly reactive derivative of chlorine with potent bactericidal properties, is used as a disinfectant in the food industry. Described as an occupational sensitizer in 1945 for the first time, it produces late or dual asthma, occasionally accompanied by fever and leukocytosis, which is mediated by IgE. We present the case of a male dairy worker who, after 4 years of exposure to the product, developed rhinitis and asthma. Skin tests with chloramine T were positive at a concentration of 10 mg/ml, while all other allergens tested negative. RAST detected specific IgE at 12 PRU and bronchial provocation induced immediate and late bronchoconstriction.