To our knowledge, this is the first case report of a 24-year-old man working in a pharmaceutical company transporting and storing raw materials who developed occupational asthma (OA) to colistin. The specific inhalation challenge confirmed the diagnosis of OA to colistin. Specific IgE was not detected, because dot-blot analysis was negative at all colistin concentrations tested. To our knowledge, OA due to a peptide antibiotic has not previously been described. This antibiotic should be listed as a trigger of OA.