This article presents information on the potential significance of the enzymatic activity of mite allergens to immunogenicity. It is reported that there has been an exciting progress in understanding the nature of the T-cell receptor, in characterizing the molecular attributes important in antigen recognition and in the genetics of atopy. The absence of complete structural information for several major allergens currently prevents a full analysis of their antigenic determinants and the possibility that there is a defective regulation of immunoglobulin E responses in certain individuals also requires further investigation.