September 17, 1999 – The hypothesis that the increase in the prevalence of allergies in recent decades is linked to a decrease in exposure to infectious agents in the first years of life may be correct.
In fact, an inverse relationship has long been observed between allergic reactions and the risk of exposure to infections at a young age. However, researchers have just published a study of 2,471 children aged 5 to 14 who had started daycare at a more or less advanced age. The results indicate that children who started daycare at an older age (between 12 and 23 months) have twice as many allergic reactions as those who started earlier (between 6 and 11 months). There are even three times more allergic reactions among those who started attending daycare after 24 months. However, this relationship disappears in the case of children from families with more than three people.
The researchers therefore conclude that infections during the early stages do indeed contribute to hampering the mechanisms of allergic reactions. This is because the stimulation of lymphocytes (a type of white blood cell involved in the reactions of the immune system) accompanying an infection inhibits the production of immunocytes specific to the allergens.
HealthPassport.net
Kramer U et al. Age of entry to day nursery and allergy in later childhoof. The Lancet, 1999; 35: 450-4.
