All environmental factors influence on the human directly or indirectly. The biggest influence has the outdoor air, which is one of the major health risk factors associated with the environment. The proportion of 9-18 % of the total hazard index of inhalation exposure belongs to formaldehyde, which has a general toxic, sensibilizing and allergic effect. The frequency of allergic rhinitis and asthma in children living in the industrial cities of Eastern Siberia is 28-36 %. The purpose of the study was to assess the individual load of formaldehyde and detection its relationship with teenagers' organism sensitization. The study was carried out on the territory of two industrial cities with high and moderate levels of air pollution. The individual hazard indices of formaldehyde inhalation exposure were calculated for 373 adolescents. The formaldehyde concentration in urine was determined by HPLC method. The leukocyte migration inhibition test to formaldehyde has been studied. The levels of secretory immunoglobulin IgA, total IgE in serum were determined by ELISA technique. The number of eosinophils in nasal mucus was calculated. Individual hazard indices of formaldehyde inhalation exposure were exceeded in all patients. Elevation of formaldehyde concentration in the urine was found in every third adolescent. More than 30 % of the surveyed had a response to the formaldehyde in leukocyte migration inhibition test, which indicates the presence of sensitization to this chemical. About 20 % of students had a combined increase of total IgE levels in the blood and the number of eosinophils in the nasal mucus and more often these cases are marked in the group of adolescents with the lowest indices of formaldehyde exposure. Reduction of the secretory immunoglobulin A was found in the serum of adolescents with increased risk indices of formaldehyde inhalation exposure.