The influence of childhood infections and vaccination on the development of atopy: A systematic review of the direct epidemiological evidence

(1) Childhood infections do not protect against atopy; on the contrary, they increase the risk of allergic diseases, in agreement to Hahnemann's observations, which included epidemic diseases among the factors capable of stimulating the development of chronic diseases. (2) Vaccination is not a risk factor for atopy, notwithstanding the allergenic effect of some vaccines.