In cool climates, the humidity circumstances in a home during the summer months are more important for allergen accumulation than those in the winter months. For the same reasons, a reduction of humidity will have a much greater impact during the summer months. Not only the relative humidity, but also the removal of the dust mites' food by cleaning can be an important factor in determining the ultimate level of mite allergens. These theoretic deductions remain to be experimentally tested. An understanding of the dynamics of mite populations and allergen concentrations in homes and public buildings is still hampered by gaps in our knowledge. These gaps mainly concern the food availability and food requirements of dust mites and the kinetics of mite allergens.