Not all medicine goes down smoothly. Each year, bad reactions or side effects send nearly 600,000 American children to hospitals or require them to get some type of medical treatment.

New research advises parents and doctors to be more vigilant when giving or prescribing drugs to children.

Daniela Menghi said she double checks with her pediatrician and the pharmacist before she gives her two young children any medication.

“Dosage was always something that really preoccupied me, knowing that you could really harm a child if you give them a little bit too much,” Menghi said.

A new study shows almost 600,000 children are treated annually for bad drug reactions, including accidental overdoses, side effects, medicine mix-ups and allergies.

“Children who are less than 5 years old were most vulnerable to those reactions,” said Dr. Florence Bourgeois with Children’s Hospital Boston.

That's because younger kids are exposed to medications for the first time. The research, based on nationwide studies spanning 11 years, showed that penicillin and other prescription antibiotics were most problematic for smaller children.

For teenagers, most bad reactions came from stimulants, anti-depressants and hormones like birth control pills.

The study found no deaths from bad drug reactions, but a large number of patients had to see their pediatrician or go to the emergency room. Five percent were hospitalized.

Researchers say parents should be more vigilant about medications for their kids, including looking for rashes, nausea, vomiting and belly pain.

“I would never forgive myself if I were trying to help my kid and I ended up doing something that would cause them more harm,” Menghi said.

Experts say medications come in many different forms and concentrations, and a bit of caution now could prevent health problems down the road. The study appears in October's issue of "Pediatrics."