Energy drinks have caused 2,000 children under six years old to be hospitalised with caffeine poisoning in the last three years.
The drinks can cause serious cardiac problems – including abnormal heart rhythms – or neurological problems such as seizures and fits.
Professor Steven Lipshultz, paediatrician-in-chief at Children's Hospital of Michigan in Detroit, said most cans of energy drink contain enough caffeine to cause a child potential harm.
He told the American Heart Association in Chicago: "Exposure to energy drinks is a continuing health problem.
"You normally think of teens and young adults as most likely to drink them, but we found that half of calls to US poison control centres involved unintentional exposures by children less than six years old."
High-caffeine energy drinks in the UK carry labels on their cans warning they are not suitable for children or pregnant women - but few retailers actively stop children buying the cans.
Prof Lipshultz said: "Energy drinks have no place in paediatric diets, and anyone with underlying cardiac, neurologic or other significant medical conditions should check with their healthcare provider to make sure it's safe to consume energy drinks."
The doctor said a child under 12 could be poisoned if they consume more than 2.5mg of caffeine for every kilogram of their body weight - enough to make most energy drinks potentially dangerous to children.
His calculations mean 50mg of caffeine in a day is enough to poison an average six year old.
A child aged 10 could get caffeine poisoning after drinking 80mg and a 12-year-old might be poisoned after 100mg.
A 500ml can of Monster Energy drink contains 160mg of caffeine - well over the limit. A 250ml can of Red Bull contains 80mg of caffeine.
A cup of strong coffee could also be dangerous, because it contains 100mg of caffeine. A 330ml can of Coca Cola, however, is deemed safe with 32mg of caffeine.
Prof Lipshultz said young children, especially those with diabetes or attention deficit hyperactivity disorder, may be particularly at risk.
He said many of the added ingredients in energy drinks have never been tested for safety in children - meaning the caffeine may not be solely to blame.
He said: "This has no place in the diet of children and teenagers, and it shouldn't be marketed at all to those under 18.
"If the goal is to try to protect the public's health, then these should be regulated similar to tobacco, alcohol and driving, so you have fewer kids winding up in the hospital or intensive care."
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