O'Connor GT, et al. - A birth cohort of high-risk inner-city children was assessed to identify early-life environmental risk factors for childhood asthma. A lower risk of asthma was found to be related to higher indoor levels of pet or pest allergens in infancy. An association was also noted between the abundance of a number of bacterial taxa in house dust and increased or decreased asthma risk. An increased asthma risk was reported in association with prenatal tobacco smoke exposure and higher maternal stress and depression scores in early life.