History of ice cream ingestion and subsequent symptoms of vomiting, bloated abdomen, are characteristic findings of lactase deficiency.Lactase deficiency -Lactase is a disaccharidase present on intestinal epithelium (brush border)*. It is used to digest lactose (disaccharide). Symptoms arise after ingestion of food containing lactose (e.g. milk). Symptom - Diarrhoea, vomiting, bloated abdomen.DiagnosisPresence of more than 1/2 percent of reducing substrate in the fresh stool.Acidic stoolsAbnormal oral sugar tolerance test* (blood glucose rise of less than 20mg/d1 above fasting level with a disaccharide load of 2g/kg) Breath H2 excretion of more than 11 ppm*. Enzyme assay on mucosal biopsies showing low levels of disaccharidases.Treatment -low lactose diet.