Rice soup is a traditional Korean food administered to control diarrhea. Useful for short-term control of diarrhea, chronic consumption of this soup can cause problems. We treated an infant who visited our hospital for symptoms of lethargy due to hypoelectrolytemia, which developed from the continuous consumption of rice soup (the upper part of rice ground in water) mixed with a spoonful of milk over a 2-month period to control frequent diarrhea. The case is reported here, together with a brief review of the literature.