Women with more children are less prone to allergies than nulliparous women and mothers of singletons

More children a woman has, the less it seems likely to suffer from allergic rhinitis or allergic conjunctivitis in his life, suggest the results of an Italian study published in the specialized "Allergy" journal.

The fact that children from large families are less prone to childhood allergies gave birth there fifteen years, in what experts call the hygiene hypothesis, recall Dr. Francesco Forastiere and colleagues.

According to this theory, fewer children are exposed to infectious agents (which is the case in a smaller siblings), plus the maturation of the immune system is directed towards the development of allergic-type responses, including the asthma or allergic rhinitis (or hay fever) belong.

Furthermore, there is evidence that maternal atopy (predisposition to develop allergic reactions) is a risk factor of allergic diseases in children.

To analyze the relationship between the number of pregnancies, number of births and the occurrence of respiratory problems (wheezing, asthma) and allergic (rhinitis or allergic conjunctivitis), Italian researchers interviewed 1,755 non-smokers aged 35 to 74 years living in four different regions.

The analysis of the testimony of participants and their medical records they found that the number of births was inversely associated with the proportion of women who have suffered at any time in their lives, rhinitis or allergic conjunctivitis.

While 30% of women do not have more than one child reported having suffered from allergic rhinitis, only 16% of mothers with more than four children were in the same situation. Similarly, the proportion of women who have been confronted with allergic conjunctivitis from 36% among women with no or one child and 17% of mothers with more than four children.

However, the authors were able to show any link between episodes of wheezing or asthma and the number of pregnancies or births.

According to Italian researchers, different hypotheses could be advanced to explain these observations. If these results are interpreted as indicating that atopy maternal influence the course of pregnancy, it can for example think that maternal atopy is associated with a "relative infertility, voluntary or not," they note.

On the contrary, if we consider that these results reflect that pregnancy itself has an impact on maternal atopy, another possible hypothesis is that the hygiene hypothesis applies to mothers as it applies to their children advance they.

Anyway, the link between the number of children and maternal allergies should be further studies and the factors that protect not only children but also their mothers, remain to be identified, the authors conclude