Nowadays, the so-called content is widespread. "hygienic hypothesis", according to which the cause of the increase in the frequency of development of atopic diseases is a decrease in the microbial antigenic load on the child's body due to a decrease in family size and d 'an improvement in living conditions. This hypothesis was formulated in 1989 by Strachan D.P. (Hay fever, hygiene and household size. BMJ. 1989 BMJ. 18 Nov 1989; 299 (6710): 1259-60). In accordance with the hygienic concept of development of allergies, infectious diseases transferred in the first two years of a child's life can have a protective effect against bronchial asthma. The fact is that reducing contact with bacterial antigens reduces the possibility of switching the immune response of Th2 cells formed in the prenatal and neonatal period with its predominance over the immune response of Th1 cells in the sense of a balanced response response. Th1 and Th2, which contributes to the persistence of the allergic response (Martinez FD, Holt PG. Role of the microbial load in the etiology of allergies and asthma. Lancet. 1999; 354 Suppl 2: SII 12 -5). There are a number of studies showing a link between early childhood infections and a reduced risk of atopy, but there is currently no direct evidence of a predisposing effect of a reduced level of exposure to antigens. bacteria on the occurrence of atopy in children.

Researchers in the UK have studied the effect of childhood infections on the development of hay fever in the future. From the General Practice Research Database (GPRD) and the Doctors Independent Network (DIN), information was obtained on 3549 comparable case-control pairs by age, sex and length of period. followed until diagnosis is established. Using this data, the researchers attempted to establish a relationship between 30 different types of infections and the risk of hay fever. Upper respiratory tract infections, diarrhea, vomiting, and acute otitis media (both listed separately), which have been transferred before the age of 2 years, have been shown to cause a moderate increase in the risk of hay fever. When the results have been adjusted for the frequency of medical visits (since children with a higher number of doctor visits are more likely to have records of infectious diseases and are also more likely to have be diagnosed with hay fever), only bronchiolitis was statistically significantly associated with a reduced risk of developing hay fever (risk ratio 0.8).

Thus, the results of this study did not confirm the concept of the protective role of infectious diseases transmitted in childhood in the prevention of allergies.