Laboratory cultures of the mites Blomia tropicalis (van Bronswijk, Cock & Oshima) and Blomia kulagini (Zakhvatkin) were used to study the population dynamics of the mites and the kinetics of released allergens during the growth cycle. The analysis of extracts obtained after different incubation periods, by means of immunoblotting, and quantification of the major allergen Blo t 5, allowed definition of three different growth phases, demonstrating that mite cultures during the maximum growth (end of exponential growth curve–beginning maximum growth plateau) contain the largest amount of allergenic components as well as the highest Blo t 5 concentration.