My 3 month old baby boy going on 4 months on July 7th just passed a gray stool his formula was changed to similac expert care alimentum for food allergies and colic on june 20th because a pediatrician said that he has a milk allergy before that he was on enfamil gentle ease and his stool was green and hard
Symptoms of milk allergy are policy pain abdomen, poor weight gain and streaks of blood in stool. I think none of the symptoms were present in your case. Green and hard stool occurs in some babies on formula feed. So I would not have changed the formula. Now on new formula observe the stool for few more days and if It's still gray then there may be some digestive problems, inform it to your doctor.