8 months old baby black stool is mainly caused by diet, in addition to breast milk and infant formula, added supplemental food baby stool is black, the first thing to consider is the supplemental food staining or baby constipation caused. If the baby has constipation, in the case of long-term failure to defecate, intestinal stool oxidation will produce dark brown. If the baby’s stool is grayish-black, it may be caused by taking iron supplements or incomplete absorption of iron from formula, or by indigestion. The latter can generally be prevented and regulated by adjusting the diet. During the regulation diet, the baby’s diet should be single and light, and he can drink rice soup and eat thin rice in moderation. After a period of conditioning, you can add a small amount of vegetables, fruit juice, rice flour, etc., but remember not to eat too much greasy, indigestible food, relatively light to eat, food to choose more easily digestible varieties. However, if the black tar-like stool, it may be more serious, this situation should be promptly brought to the hospital, follow the doctor’s advice for treatment.