Several studies have proven the important influence that environmental exposures have in the individual's susceptibility to suffer allergy and other related diseases, mostly during embryonic or early life. Although the relationship between the environment and allergic diseases had been previously reported, one interesting attempt to describe this relationship was Strachan's hygiene hypothesis, proposed almost two decades ago. Since then, several studies have identified new environmental factors related to an increased risk of allergic disease. In this context, epigenetic modifications appear as a possible link between the environment and genome, providing a plausible mechanism for explaining how the recent changes in lifestyle can modify gene expression, and thus, lead to a disease state. Here, we will focus on the environmental modifiers that have been described and the possible role of epigenetic modifications.