The health system is one of the professional sectors perhaps most at risk of occupational asthma. The aims of this study were to evaluate the level of knowledge of health care workers (HCWs) on occupational asthma and asthmogenic agents and to pave the way to effective educational action on the subject.A multicenter transversal study including 180 HCWs was carried out between July and December 2020. A validated questionnaire addressed four dimensions: knowledge of asthmatic disease, knowledge of occupational asthma, knowledge of prognosis of occupational asthma and knowledge on the prevention of occupational asthma.The average total score was 13.71/18 (76.17%). There was no correlation between average total score and age, educational level, seniority or status of paramedical staff. Mean total scores were significantly higher for participants with no fixed work schedule and those practicing in non-university structures. The difficulty indexes for the four aforementioned dimensions were 82.22%, 77.56%, 53.52% and 66.67% respectively.Knowledge gaps affect all professional categories but to different degrees. A review of the level of knowledge of persons in each category would be the first step on the road to planned educational action.