Feces in infants comes in different colors and consistencies. Formula-fed babies commonly produce bowel movements that are yellow, tan or brown, whereas breast-fed babies typically produce mustard-yellow bowel movements. Green feces in infants can have several causes, such as changes in eating habits, illness or from food intolerance.
Meconium, which Medline Plus notes is made up of amniotic fluid, mucus, bile and skin cells, is a thick, sticky substance that is passed during bowel movements in the first few days of an infant's life. Meconium can be green or black and contains fine hair from the infant's body. After four or five days the meconium will pass and the infant will start to produce green or yellow feces.
Normal Green Feces
Introducing solid foods into an infant's diet can change the color of his bowel movements. The consistency and smell of the feces may also change, and more frequent bowel movements can occur. Mayo Clinic states that food dyes and green vegetables, such as spinach, are common causes of green stools, and Web MD notes that consuming too much sugar and starch can cause loose, green feces.
Non-Life Threatening Instances
Too much iron in baby formula can cause an infant's bowel movements to become dark green. In breast-fed babies, watery-green colored bowel movements are an indication that the infant isn't consuming enough high-calorie breast milk. A mild illness can also change the color and consistency of an infant's bowel movements, and green colored feces in both breast-fed and bottle-fed babies can indicate a mild infection or a food intolerance.
MayoClinic.com states that severe diarrhea, which can be serious in infants because of the likelihood of dehydration, can cause feces to be loose and green. Green feces that is watery and foul smelling can indicate an intestinal infection or a food allergy. If an infant has green stools and also develops other symptoms such as a fever, a skin rash or a high temperature, medical attention must be sought immediately.