New research shows more than half a million children have bad reactions from prescription drugs
Children younger than age five are most commonly affected.
Penicillin and other prescription antibiotics are among drugs causing the most problems.
The study is based on national statistics on patients' visits to clinics and emergency rooms in a 10-year span.
Officials say parents should pay close attention when their children begin taking a medication for the first time. Also doctors should tell parents about possible signs of an allergic reaction.
The data showed no deaths, but five percent of children were sick enough to require hospitalization.