Antigens from house dust mites are the most important indoor allergen involved in the immunopathogenesis of perennial allergic rhinitis and asthma. Storage mites have been identified in the dust of homes in many tropical and temperate climates. The role of these mites in allergic respiratory conditions needs to be clarified. We studied sensitivity to the storage mites Biomia tropicalis and Tyrophagus putrescentiae in patients previously considered non-allergic, based on negative reactions to skin tests with common inhalant allergens in our region. It was possible to verify that some of these patients were in fact sensitized exclusively to the storage mite allergens.