Allergic reactions among sisal processing workers

Introduction 
Respiratory symptoms, particularly byssinosis, have been described among workers handling sisal fibers. A few studies have described immunological properties of sisal, but no detailed studies have been performed to identify the possible allergen molecules in sisal leaves.

Methods 
We performed a cross sectional study involving 138 male sisal workers in Tanzania to examine IgE sensitization related to sisal exposure during processing of sisal leaves. City dwellers (n=78) who had never lived close to sisal estates or worked with sisal were used as controls. Skin prick tests (SPT) were done according to EAACI standard guidelines using dry sisal fibers and fresh sap from harvested sisal leaves. In addition we analysed sisal leave extracts in order to identify possible allergen proteins by using SADE PAGE electrophoresis and immunoblotting. 

Results 
Sisal processing workers had worked in sisal industry for a mean of 13 years, and were significantly more likely to be smokers than the control group. The sisal workers did not use any respiratory or skin protective devices. Sisal exposed workers had significantly higher prevalence of positive SPT and larger wheal reactions than controls. Sensitization to fresh sisal sap by SPT was 4 times higher among sisal workers (60%) compared to controls (15%). Similarly for dry sisal fibers sensitization by SPT was much higher among sisal workers (30-40%) when compared to controls (3%). Possible sisal allergen molecule(s) were visualized at 45-46 Daltons. 

Discussion 
Sisal processing workers exposed to sisal through inhalation and skin contact were more likely to be sensitized to the sisal than controls. These findings may be caused by possible allergens in sisal leaves. However; the cross sectional design makes the casual relationship difficult to ascertain. More comprehensive studies are needed in this area.