Epidemiology of childhood urticaria and especially that of infants is badly understood because of a lack of studies devoted to this age group. A retrospective study of 40 infants that were hospitalised for urticaria has been made to clarify the factors that produce urticaria at that age. Certain clinical signs seem to be more frequent at this age, such as the bruised appearance of the lesions. Acute urticaria is the most frequent form. An etiology has been confirmed or suspected in 2/3 cases: intolerance of cow milk proteins before 6 months, drug and infection causes after 6 months. Prospective studies of infantile urticaria are necessary.