It has been shown that early sensitization (including that to mite and cat) is crucially important for the development of asthma,42, 43, 44, 45 and our finding that the interactions between FLG and cat and mite exposure in relation to specific sensitizations are stronger in early life might be one of the mechanisms by which FLG loss-of-function mutations increase the risk of asthma.24 Here, FLG is linked to asthma.