Asthmatic children who are exposed to cigarette smoke are more likely to make repeat trips to the hospital for breathing problems. But researchers say asking parents about kids' smoke exposure may not yield the most reliable information.

In a recent study, saliva revealed exposure to tobacco smoke in roughly 80 percent of children brought to the hospital for asthma or breathing problems. But only about a third of parents said their children came in contact with smoke.

What's more, finding evidence of nicotine, a chemical in tobacco, in children's saliva was a better predictor of whether they would need to come back to the hospital, compared to the information parents gave to doctors.

"We think saliva is a good and potentially useful test for assessing an important trigger for asthma," said Dr. Robert Kahn, the study's senior author.

Previous research has found that being exposed to tobacco can lead to airway problems and poor asthma control among children, Kahn and his colleagues wrote in the journal Pediatrics.

By figuring out which children are being exposed to tobacco, doctors may be able to step in and identify and possibly eliminate the exposure, said Kahn, a pediatrician at Cincinnati Children's Hospital Medical Center in Ohio.

Read more from Reuters.