NEW YORK (Reuters Health) - Babies younger than six months old should never be given water to drink, physicians at Johns Hopkins Children’s Center in Baltimore remind parents. Consuming too much water can put babies at risk of a potentially life-threatening condition known as water intoxication.

“Even when they’re very tiny, they have an intact thirst reflex or a drive to drink,” Dr. Jennifer Anders, a pediatric emergency physician at the center, told Reuters Health. “When they have that thirst and they want to drink, the fluid they need to drink more of is their breast milk or formula.”

Because babies’ kidneys aren’t yet mature, giving them too much water causes their bodies to release sodium along with excess water, Anders said. Losing sodium can affect brain activity, so early symptoms of water intoxication can include irritability, drowsiness and other mental changes. Other symptoms include low body temperature (generally 97 degrees or less), puffiness or swelling in the face, and seizures.

“It’s a sneaky kind of a condition,” Anders said. Early symptoms are subtle, so seizures may be the first symptom a parent notices. But if a child gets prompt medical attention, the seizures will probably not have lasting consequences, she added.

Water as a beverage should be completely off limits to babies six months old and younger, Anders and her colleagues say. Parents should also avoid using over-diluted formula, or pediatric drinks containing electrolytes.

Anders said it may be appropriate in some cases to give older infants a small amount of water; for example to help with constipation or in very hot weather, but parents should always check with their pediatrician before doing so, and should only give the baby an ounce or two of water at a time.

If a parent thinks their child may have water intoxication, or if an infant as a seizure, they should seek medical attention immediately, she advised.