All Rights Reserved. Dark green or green-black poop in babies is commonly caused by iron supplements or iron-fortified formula. Even though a drop or two of food coloring is enough to turn a beer green, it's likely not enough to have noticeable results in the toilet. Green poop isn't always a cause for concern, but sometimes it may indicate an underlying health condition. If people have stools that are dark red, black or tarry, or bloody, they should seek emergency medical attention.
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