We have previous presented a study of the cytotoxic effect of untreated and heat-treated cotton dust. The lipopolysaccharide (LPS) content in heat-treated cotton dust was reduced by 73% compared to untreated cotton dust. We found a slightly higher cytotoxic effect of the heat-treated cotton dust compared to untreated cotton dust. We investigated the content of mold spores in the two dust samples and found nearly the same species in both samples. The aim of this project was to test if components of the molds still remaining in the heat-treated cotton dust might cause the cytotoxic effect. We have tested the cytotoxic effect of b 1-3-D-glucan and Patulin, a mycotoxin produced by several Aspergillus and Penicillium species. Patulin showed a cytotoxic effect after 24 hours of incubation with concentrations in the range of 1-100µg/ml. The effect of the mycotoxin was significantly higher than the effect of cotton dust. Hence, if Patulin is present on cotton it might explain the cytotoxic potentiale of the dust. But we don't know if these mycotoxins are present in concentrations high enough to induce these effects.