Efforts to evaluate the roles and overall levels of allergens carried by microaerosols remain preliminary. It is not clear what range of allergen specificities may yet be recovered from small particle fractions under suitable analysis. However, it now appears that airborne units sized below 10 μm may contribute, perhaps substantially, to inhaled allergen burdens. Innovative application of filters and high speed impingers, as well as of immunoassays, should increasingly clarify the clinical roles of such previously overlooked, small aerosols.