KANSAS CITY, Mo. -- An 18-month-old girl has her 3-year-old sister to thank after surviving swallowing a toxic lithium battery.

The parents of 3-year-old Bailey and doctors are calling her a hero after she helped keep her younger sister from being more seriously injured.

On Halloween night the girls' dad was carving pumpkins and rather than risk a fire, he used LED candles powered by lithium batteries.

"She crawled up and grabbed one of the batteries and swallowed it," mother Sarah Thompson said.

Sarah said Bailey saw the whole thing and even at 3 years old, knew something wasn't right.

"She went back to bedroom and told my husband what happened, 'Daddy, Daddy, she swallowed a penny!" Sarah said.

The battery got stuck in Shelby's esophagus. After only a short time, the outer coating had completely eroded.

Doctors at Children's Mercy Hospital removed the battery before it caused serious injuries.

Sarah and her husband said they never knew how dangerous a tiny battery could be and want other parents to be aware.

"We're getting a message out there to other parents," Sarah said.

Bailey's preschool is giving her an award next week and will use what happened to her to teach other kids a lesson about looking after little brothers and sisters.