Pediatricians at Hopkins Children's see at least three or four such cases every summer, and while the seizures are benign and have no lasting effect on a child's health, they are quite dramatic and completely preventable, doctors say.

"Babies need extra fluids in the hot weather, but straight water is not one of them," says pediatrician Allen Walker, M.D., head of the Emergency Department at Hopkins Children's. "A parent's natural instinct is to give the baby water to prevent dehydration, but too much water can disrupt the delicate balance in a baby's body, leading to water intoxication. Before you know it, the baby is seizing."

Too much water dilutes sodium in the blood and flushes it out of the body, thus altering brain activity, which can lead to a seizure. Infants under 1 year of age may be more prone to these types of seizures than older children because a young infant's diet does not contain enough food sources to replenish the lost sodium. Also, an infant's immature kidneys cannot flush out excess water fast enough, causing a dangerous buildup of water in the body.

Breast milk and formula are the best way to keep a child under 1 year of age who is not eating solid foods hydrated, Walker says, and straight water should be avoided. Over-diluted formula can lead to water intoxication as well. Electrolyte-enriched pediatric drinks are not recommended for routine hydration.

Symptoms of water intoxication in an infant include:

changes in mental status, i.e., unusual irritability or drowsiness low body temperature, usually 97 degrees or less facial swelling or puffiness seizures

Though any infant who consumes too much water can suffer water intoxication, the risk is highest among children who are already dehydrated, typically after a bout with viral or bacterial infections that cause vomiting and diarrhea. Symptoms of dehydration in a young child include dry mouth, increased thirst, irritability and reduced sweating and urination. An easy way to spot dehydration is if a child has fewer than three wet diapers in 24 hours, Walker says.

In otherwise healthy infants, water intoxication is one of the leading triggers of seizures. The most common type of childhood seizures are febrile seizures, occurring in 2 to 5 percent of all children under 5 years of age, according to the American College of Emergency Physicians.

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