Dermatophagoides pteronyssinus (Dp), Dermatophagoides farinae (Df), Euroglyphus maynei (Em) and Blomia tropicalis (Bt). Over the past three decades, many important allergens from these species have been identified and characterized at the molecular level. The biological function of several house dust mite allergens has been elucidated, with many of them showing enzymatic activity. However, Bt allergens remain the least studied, even though this mite is very common in tropical and subtropical regions of the world, including Puerto Rico. Therefore, it is very important to include Bt in diagnostic and therapeutic strategies for house dust mite induced allergy and asthma, particularly in areas where Bt exposure and sensitization is high. Recombinant DNA technology, as well as other molecular biology and immunological techniques, have played a fundamental role in advances towards a better understanding of the biology of house dust mites and their role in allergic diseases. This kind of study also contributes to the understanding of the complex immunologic mechanisms involved in allergic reactions. The development of effective diagnostic and therapeutic approaches depends on the continuity of research of house dust mite allergens. The objectives of this review are to describe the most important aspects of house dust mite allergy and to acquaint the scientific community with the latest findings pertaining to house dust mite allergens, particularly those derived from Bt.