Pediatricians at Johns Hopkins Children’s Center say it may not be the best choice for babies. In fact, drinking water can be harmful for babies younger than six months of age, and can possibly lead to water intoxication and even seizures.

Signs and symptom
Apparently, water can dilute sodium in the infant’s blood and flush it out of the baby’s system. This causes brain activity to change, which can cause a seizure. Because babies younger than 1 year of age often do not have many sodium-containing foods in their diet, they may be more vulnerable to this condition. In addition, because their kidneys are immature, they often have trouble flushing out the water they imbibe.

The signs of water intoxication are subtle, so parents may not be aware that a problem is developing until their babies reach the point of seizure. Specifically, symptoms include:

• unusual irritability
• drowsiness
• low body temperature (97?F or less)
• facial swelling or puffiness
• seizures
  

Children who have recently been dehydrated, such as those who have had a recent bout of diarrhea and/or vomiting, are at greatest risk for water intoxication. Symptoms of dehydration include:

• unusual irritability
• increased thirst
• dry mouth
• reduced sweating
• fewer than 3 wet diapers in 24 hours
  

Parents should be reassured that, if an infant receives prompt medical care, the seizures that result from water intoxication are usually benign, without long-term effects on the infant’s health. Prompt medical care is important, though; Dr. James P. Keating of Children’s Hospital St. Louis points out that extreme [albeit rare] cases of water intoxication can result not only in seizures but also coma, brain damage, and death.

What’s a parent to do?
When temperatures climb and everyone feels hot, it seems second nature for parents to share their thirst-quenching water with their little ones. It’s true that babies do get thirstier in the heat, just like adults, and they need additional fluids. But don’t give them water. Instead, breastfeed them more or give them formula. (But, if you’re formula-feeding be careful: over-diluted formula can also cause water intoxication. Pediatric electrolyte drinks should also be avoided.)

If your child’s pediatrician does recommend that you give your baby water (for example, to help with constipation), avoid giving more than one to two ounces at a time. Also, be sure to give it after meals, so it is less likely to interfere with the nutrition your child receives.

In short: When it’s hot outside, do what you usually do when your baby is thirsty—breastfeed or formula-feed—just do a little more of it.