The MAS is an observational, population-based, allergy-risk-enriched cohort of newborns enrolled in Germany in 1990. Assessments of various lifestyle and environmental exposures took place at 19 points, including 9 clinical visits for physical examinations and biosampling up to the age of 20 years. A total of 1,314 out of 7,609 infants born in 1990 were recruited in 6 university hospitals from 5 German cities (Berlin, Düsseldorf, Mainz, Freiburg, and Munich). A total of 499 newborns with risk factors for allergic diseases (i.e., increased cord blood immunoglobulin (Ig) E > 0.9 kU/L, or at least 2 atopic family members) as well as 815 newborns with none of these risk factors were included in the cohort. These children were assessed at birth and followed up at the ages of 1, 3, 6, 12, 18, and 24 months, and from then on yearly within 4 weeks of the child's birthday up to age 13, then at 15, and again at 20 years.