Whenever you see blood in your baby’s poop you need to be concerned; however, the blood may come from a cracked nipple during breastfeeding in which case you will need to treat the condition. What looks like blood may also be food coloring from foods like beetroot if your baby is on solids or it may be an allergy to something in your diet. But, if you are unsure of the reason then it's best to see your doctor as soon as possible.