Of eighty African asthmatics, sixty-three had significant levels of specific IgE against the house dust mite Dermatophagoides pteronyssinus. By contrast, grass-specific IgE was found in six patients and mould-specific IgE in none. Sixty-three patients also had symptoms predominantly during the rainy season.

Positive skin tests against D. pteronyssinus correlated well with the presence of mite-specific IgE, as did the size of these skin test weals with the amount of specific IgE. For grass pollen and moulds there was no such relationship. There was no correlation between a history of sensitivity to house dust and either skin tests or specific IgE against D. pteronyssinus.

The results support previous findings that it is allergy to house dust mite and not to grass pollens or moulds which is important in producing the seasonal symptoms in our patients.