A 7-month-old boy on an oligoantigenic diet because of multiple food intolerances presented with anorexia, failure to gain weight and severe hypochloremic metabolic alkalosis with hyperreninemia. Clinical symptoms and biochemical abnormalities disappeared after adequate dietary supplementation with potassium and sodium chloride. This case emphasizes that minimal daily mineral requirements must be provided in infant diets, and highlights the risk of nutritional deficiencies inherent in the prolonged use of oligoantigenic diets not adequately supplemented.