No abstract

No abstract

No abstract

After the publications of the studies (Voorhorst et al. 1964; in which we demonstrated that the allergenic component of house dust is a substance produced by the mite Dermatophagoides pteronyssinus many investigators asked us for samples of extracts of these mites for experimental purposes. The results obtained by most of them have confirmed our finding that this and other species of Dermatophagoides produce a very potent allergen to which very many asthma patients have become sensitized. However, many of these investigators obtained fewer positive reactions to Dermatophagoides than to house dust extract. We think that the reason for this discrepancy may lie in the fact that these investigators had not made the two kinds of extracts equally strong. It may be that the scarcity of the mite material induced them to keep the extracts, which are rather unstable, too long in a too diluted form. Another possible reason is the following. Although we sent all these investgators not only the mite material but also a house dust extract that could be made equally strong, many of the recipients did not follow our advice and used not our house-dust extract but one prepared by themselves. Since our standard house dust extract is rather weak, most investigators obtained more skin reactions and more "positive" provocation tests with their own generally stronger house dust extracts than with the Dermatophagoides-cuXtuvt extract standardized to our extract. It is quite obvious that more concentrated ex-

No abstract