It’s a question that a lot of new parents ask themselves, especially when they might be receiving outdated advice from well-meaning but incorrectly informed friends and family: Do babies need to drink water?

The answer is no: According to the The American Academy of Pediatrics (AAP), babies under 6 months old should not be offered water.

Babies can get all the hydration and nutrition they need from breast milk or formula for their first six months of life. But why can’t babies drink water? In a now-viral TikTok stitch that’s been viewed more than 3 million times, pediatrics resident @dr.emzieees explains why giving babies water can actually be dangerous.

@dr.emzieees #stitch with @bimbotheclown ♬ original sound – Dr.emzieees

“Babies cannot have water before six months. Why is that? Because water has no sodium. And you know what will happen, is the water gets into their blood and it dilutes their blood and they can become hyponatremic or low-sodium. They will get water poisoning very, very, very quickly,” she explains.

Related: How to give a baby a bath, in 5 simple steps

What is water poisoning or water intoxication?

Water poisoning, also known as water intoxication, can happen when the kidneys are given more water they can handle, and the excess water ends up in the bloodstream, altering the blood’s electrolyte balance. Because the kidneys are still developing in babies under 6 months, they’re not as well-equipped at processing water, which can make young babies more susceptible to water intoxication.

If your baby shows any of these signs of water intoxication, head to the hospital immediately:

  • Inconsolable crying
  • Vomiting
  • Lethargy
  • Seizures
  • Tremors

When can babies have water?

Babies’ only drink (and only form of food or nutrition) should be breast milk or formula until they turn 6 months old, notes @dr.emizeees, in line with AAP guidelines, at which point they can start to have small amounts of solid food and water.

That means parents and caregivers should only feed babies breast milk or formula in any prepared bottles (no water, no juice, no infant cereal) unless they are directly advised to serve another liquid by a physician.

Even on hot days, parents don’t need to feed babies water. Bottle-fed babies may require more frequent formula feeds during hot weather in order to stay hydrated and breastfeeding babies may want to nurse more than usual if it’s hot out, but water should not be offered until they are at least 6 months of age.

If you have any questions about your baby’s hydration and nutrition, don’t hesitate to ask your pediatrician or health care provider.

A version of this story was originally published on Nov. 15, 2019. It has been updated.