Why Is My Baby's Poop Green?

Illness

If the green stool looks like diarrhea or contains mucus, something is probably irritating your little one. "Sometimes babies get a stress reaction, or it could be a stomach bug," says Dr. Palmer. If this happens, 

maintain your regular feeding schedule as your baby will tolerate it; breast milk provides antibodies that promote recovery and your little one will need to stay hydrated.

Green foods

Nursing infants and children may have green baby poop if the lactating person eats leafy greens or green food coloring. Once your child starts eating solids, green foods (like peas or spinach) can also tint their stool.

Iron supplements

"Dark green baby poop after the first few days of life is probably from an iron supplement," either taken by the [birthing person] or the baby, says Dr. Palmer.

Insufficient milk intake

If a nursing baby isn't getting enough milk, they might have small but infrequent green poops—though most babies simply won't dirty their diaper regularly (newborns should poop at least 3–4 times each day),

 won't gain weight, and may act fussy or sleepy. Call your pediatrician or lactation consultant right away if you're worried your baby isn't eating properly.

Food intolerance

According to Dr. Palmer, a cause of green baby poop could be food intolerance—either to something in breast milk or the baby's formula— though this isn't typical. Most babies will present with blood in their stool or red poop from food intolerances. "The number one ingredient that babies react to is cow's milk," says Dr. Palmer, although many other foods, beverages, or medications could cause a reaction. If your baby has a food intolerance, they may also develop eczema and act irritable after feeding.