OBJECTIVETo analyze possible risk factors for diarrhea in breast fed infants and provide evidences for prevention and treatment of diarrhea, reducing allergic and other diseases in infants and for renewing the definition of "physiological diarrhea".

METHODSTotally 334 infants (207 boys and 127 girls, mean age 3.0 +/- 0.4 months) who were solely breast fed and seen between August 2004 and June 2006 at the outpatient clinic of the Department of Pediatrics, the 3rd Hospital of Peking University were enrolled in this study. The following information concerning parental and the infants' possible risk factors was obtained through a questionnaire that included parents' age, education, smoking, alcohol consumption, weight, height, maternal pregnancy weight, weight gain and health status during pregnancy and family history of hypersensitivity, family history of digestive tract disease, diet of mother in lactation, the infants' age, height, weight, head circumference, chest circumference, rash, eczema, diet, vomiting, abdominal distention, and blubber. The levels of PGE(2), fat and lactose in breast milk, serum allergen and skin prick test were performed in all the 334 infants. Logistic regression analysis was performed by using the software SPSS 10.0.

RESULTSMaternal smoking (OR = 2.3), hypersensitivity (OR = 2.7), family history of hypersensitivity (OR = 2.8), diet of mother included seafood (OR = 1.8), egg (OR = 2.3) and peanut (OR = 2.0), infants' eczema (OR = 2.9), blubber (OR = 2.7), high level of PGE(2) (OR = 2.4) and fat in breast milk (OR = 3.0), serum allergen positive (OR = 4.0), positive skin prick test (OR = 2.7) were the risk factors for diarrhea in breast fed infants (P < 0.05).

CONCLUSIONSDiarrhea in breast fed infants is not a simple physiologic process. It may be associated with many factors and the underlying mechanism remains to be clarified via further studies.