Recurrent episodes of vomiting and dehydration in an infant or young child suggest the possibility of an inborn error of metabolism, particularly organic acidemias and urea cycle disorders. Similar patterns are seen in cyclic vomiting syndrome, which is most common in school-aged children. Migraine also may present with periodic vomiting, but can usually be distinguished by the family history of migraine and associated headache. (See 'Inborn errors of metabolism' above and 'Cyclic vomiting syndrome' above and 'Migraine' above.)