With regard to the comments by Kolbe et al 1 concerning life threatening exacerbations in asthmatic patients, we would like to make the suggestion that a major cause is failure to check that drug delivery still contains active drug.2 ,3 The use of lactose, although unpleasant to take, is a good indicator of the presence of an active drug, better than the alternative of a visual indicator. The recent admission of a 13 year old boy with a severe asthmatic attack to our intensive care unit demonstrated this fact. He had been using a fully expired budesonide Turbuhaler for 2 weeks prior to his admission. In view of this problem, it may be prudent to add lactose rather than a visual indicator system to inhalers.