This article is a commentary on the following study: Gent JF, Ren P, Belanger K, Triche E, Bracken MB, Holford TR, Leaderer BP. Levels of household mold associated with respiratory symptoms in the first year of life in a cohort at risk for asthma. Environ Health Perspect. 2002 Dec;110(12):A781-6. Fungi and molds are ubiquitous allergens in our environment. The association between mold exposure and asthma or respiratory symptoms is well-known, but the causality of this association is debated. The objective of this study was to estimate the relationship between exposure levels to certain molds and the onset of symptoms (wheezing and chronic cough) in a cohort of children at risk for asthma. In many studies, mold exposure has been assessed using questionnaires, and there is not necessarily a correlation between the presence of visible mold reported in interviews and objective measurements of mold in air or dust samples. This prospective study of a birth cohort with a single-point measurement of mold in the home environment is therefore of interest and appears to confirm the link between early exposure to Penicillium and the risk of asthma. This study does, however, have certain limitations. (Excerpt from the article)