Sulfites are compounds which are mainly used in the agricultural, food and pharmaceutical industry as preservatives. The possibility of manifestations of acute hypersensitivity appearing after the ingestion or inhalation of sulfites has already been described several times, over the past twenty years. Amongst these manifestations and indeed the one that is most often present is bronchospasm, which can sometimes be severe. A few cases of occupational intolerance through contact eczema to sulfites have also been published. The idea of occupational asthma to metabisulphates is, on the other hand, extremely recent; its legal recognition only dates back to 1989. The authors present three new cases of occupational asthma to metabisulphites stressing the value of a specific provocation test and the different hypotheses for the pathogenesis of the disorder are reviewed. Preventative measures are always preferable to avoid the development of severe occupational asthma. In all cases, notification of occupational asthma is necessary.