She is one of the first allergy researchers who found out after the fall of the german wall in 1989/90 that in the GDR, despite the poorer environmental conditions caused by the air pollution, proportionately only half as many allergies existed as in the Federal Republic of Germany. After the reunification, the same level in both parts of the country was reached within a few years. Erika von Mutius suspected that the children had more contact with other children through their daycare in kindergarten. She stated in comparative studies that despite higher air pollution in Leipzig compared to Munich, the risk of asthma in children was not higher. She also found that children who grow up in the countryside and who are in contact with animals have a lower risk of allergies.