Cow's milk protein allergy is a growing problem in developed countries. We report the case of a Chinese infant, born at term, who presented on day 28 with severe growth failure, chronic diarrhoea, and metabolic acidosis. Investigations supported a diagnosis of cow's milk protein allergy. This was confirmed by withdrawing and reintroducing the relevant infant formula under controlled clinical conditions. Both acidosis and diarrhoea were seen to resolve, and 'catch-up' growth was evident after introduction of an elemental infant formula. Early recognition of this problem leads to a rapid 'cure', as seen in this case. However, later presentation with other atopic conditions has been reported.