There is evidence that in very young children with recurrent wheezing there are increased numbers of macrophages and neutrophils in the airways, rather than the oesinophils and mast cells of later asthma. This has been interpreted as suggesting that bacterial infection may play an important part in the early stages of childhood asthma. Now researchers in Copenhagen (Hans Bisgaard and colleagues. New England Journal of Medicine 2007;357:1487–95; see also editorial, ibid: 1545–7) have demonstrated an association between early asthma and throat colonisation with bacterial pathogens at 1 month …