Method of creating an homogeneous allergen-laden atmosphere in an exposure room whose concentration in allergens C exposure and MMAD (mass median aerodynamic diameter) of the allergens D exposure are previously chosen, which method is characterized in that implementation is carried out by means of an ultrasound nebulization device, from an aqueous composition of allergens and an airflow devoid of allergens having a constant flowrate d air; in that, it includes the following steps: - the values C exposure and D exposure, to be obtained to within a tolerance in the atmosphere of the exposure room, are chosen; - depending on the chosen value D exposure, the frequency F at which the ultrasound nebulization device is to be made to operate and the concentration in allergens C composition that the aqueous composition of allergens must have, to obtain in the atmosphere of the exposure room an allergen MMAD corresponding to the chosen value D exposure to within the tolerance, are determined, - depending on the chosen value C exposure, on the flow rate d air of the airflow devoid of allergens, on the efficiency of the ultrasound nebulization device and on the determined allergen composition C composition, the flowrate d composition, with which the aqueous composition of allergens is to be introduced into the ultrasound nebulization device to obtain in the atmosphere of the exposure room an allergen concentration corresponding to the chosen value C exposure to within the tolerance, is determined, - the aqueous composition of allergens is supplied or prepared with the determined allergen concentration C composition, - the aqueous composition of allergens is introduced, with the determined flowrate d composition, into the ultrasound nebulization device operating at the detemined frequency F, - from the aqueous composition of allergens and by means of the ultrasound nebulization device, a moist nebulisate is formed, made up of droplets of the aqueous composition of allergens in suspension in the air, - the moist nebulisate is dried by means of a drying airflow to obtain a dry nebulisate, made up of solid allergen particles in suspension in the air, - the dry nebulisate is mixed, outside the exposure room, with the airflow devoid of allergens having the flowrate d air, to obtain an allergen-laden airflow, - the allergen-laden airflow is introduced into the exposure room, through at least one diffusion vent located in the upper part of the exposure room, - the allergen-laden airflow is drawn out of the exposure room through at least one exhaust vent located in the lower part of the exposure room. - the values C exposure and D exposure, to be obtained to within a tolerance in the atmosphere of the exposure room, are chosen; - depending on the chosen value D exposure, the frequency F at which the ultrasound nebulization device is to be made to operate and the concentration in allergens C composition that the aqueous composition of allergens must have, to obtain in the atmosphere of the exposure room an allergen MMAD corresponding to the chosen value D exposure to within the tolerance, are determined, - depending on the chosen value C exposure, on the flow rate d air of the airflow devoid of allergens, on the efficiency of the ultrasound nebulization device and on the determined allergen composition C composition, the flowrate d composition, with which the aqueous composition of allergens is to be introduced into the ultrasound nebulization device to obtain in the atmosphere of the exposure room an allergen concentration corresponding to the chosen value C exposure to within the tolerance, is determined, - the aqueous composition of allergens is supplied or prepared with the determined allergen concentration C composition, - the aqueous composition of allergens is introduced, with the determined flowrate d composition, into the ultrasound nebulization device operating at the detemined frequency F, - from the aqueous composition of allergens and by means of the ultrasound nebulization device, a moist nebulisate is formed, made up of droplets of the aqueous composition of allergens in suspension in the air, - the moist nebulisate is dried by means of a drying airflow to obtain a dry nebulisate, made up of solid allergen particles in suspension in the air, - the dry nebulisate is mixed, outside the exposure room, with the airflow devoid of allergens having the flowrate d air, to obtain an allergen-laden airflow, - the allergen-laden airflow is introduced into the exposure room, through at least one diffusion vent located in the upper part of the exposure room, - the allergen-laden airflow is drawn out of the exposure room through at least one exhaust vent located in the lower part of the exposure room.