Allergic asthma, rhinitis, rhinoconjunctivitis and atopic dermatitis are the most common allergic disorders that are caused by the house dust mite (HDM). Beside pyroglyphid mites, the clinical importance of non-pyroglyphid mites has also been increasingly recognized in the recent years. Blomia tropicalis is the most important and ubiquitous mite species in tropical and subtropical regions of the world. Well-standardized and characterized allergens are essential for the diagnosis and therapy of house dust mite allergy as well as for the study of the pathophysiology of allergic disease. With the introduction of molecular biology, a number of house dust mite allergens were obtained by cloning the genes encoding the allergens. To date, seven allergens from Blomia tropicalis have been identified and characterized. Among these, Blo t 5, with unknown function, is the major allergen of Blomia tropicalis, with up to 92% of allergic patients sensitized to it. Native Blo t 5 has been purified and shown to consist of multiple isoforms. With advancing knowledge of these specific allergens, it is anticipated that targeted, effective, diagnostic, efficacious and safe therapeutic modalities would be developed.