“Our study shows that individuals that were breastfed as babies have an increased risk of developing hay fever and eczema, while breastfeeding doesn’t seem to have an effect on asthma,” says Weronica Ek, researcher at Uppsala University’s Department of Immunology, Genetics and Pathology, who led the study. The data also show that increased socioeconomic status lowers the risk of asthma while it increases the risk of developing hay fever. These results are in line with the ‘hygiene hypothesis’, which states that growing up in a cleaner environment increases the risk of being diagnosed with allergies due to a lack of early childhood exposure to microorganisms, among other things. This study also shows that a high BMI increases the risk for asthma, hay fever and eczema, while the risk decreases in individuals with higher birth weight. It is important to remember that this study is an observational study, which does not allow for clinical recommendations to be made. In such studies there may always be underlying factors that the researchers do not have information about, which are the true causes of the observed effects. For instance, mothers who have the studied diseases themselves may have been recommended to breastfeed or not to breastfeed, which may affect the findings of the study. It is well established that breastfeeding has a positive effect on the health of the baby. Even though we do not see a protective effect of breastfeeding on the risk of developing asthma or allergies, these results should not be used to recommend or discourage breastfeeding since the present study only investigates the effect of breastfeeding on allergies and asthma. “However, we hope that our study can give a more correct picture of the health benefits of breastfeeding,” says Weronica Ek.