Moulds and yeasts, which contribute to an increased risk of chronic asthma and allergy, are far more common in indoor daycare centres than they are found outside.  According to a recent research published in Applied and Environmental Microbiology by a team led by Eva Lena Estensmo at University of Oslo, certain building features and the number of children in a daycare centre influenced the species of fungi found within, indicating that many of the moulds and yeasts probably have indoor sources. The researchers analysed the indoor and immediate outdoor mycobiomes of 125 daycare centres in Norway, sampling dust swabs from inside daycare buildings, and correlating the findings with the number and ages of children, the building type, material, ventilation types, presence of pets etc. The surprising diversity in yeasts could be due to young children bringing in organic materials such as soil and litter from nature, compared to other indoor environments.