TORONTO — When a child wakes up with a deep, barking cough, it could be croup. A common treatment is sitting in a steamy bathroom with the child on your lap. A new study that shows humidity may not really help at all.

Recently, Stephanie Greer woke up to the sound of an awful, barking cough. Two-year-old Kyan had the croup -- a viral infection in the airway and voice box.

"It's a curious seal-like cough or something like a dog trying to clear its throat," said Dennis Scolnik, of the Toronto Hospital for Sick Children.

Greer said she did what most parents do.

"I kind of just turned on everything and sat by the shower," she said. "It did get humid in there but I don't know. I didn't think it was doing too much for him."

It probably was not helping Greer's son, according to a new study in the Journal of the American Medical Association.

"Our study looked into the effect of different kinds of humidity in the treatment of croup," Scolnik said.

Over three years, researchers studied 140 children -- ages 3 months to 10 years -- who had severe croup.

"In this particular group of patients, humidity had no positive effect in treating their croup symptoms," Scolnik said.

Using masks, the children were treated with different humidity levels and specifically sized water particles.

"Humidity in any form -- however well you've prepared it, however exactly you're trying to deliver it to the area that's affected by croup -- didn't have an effect," Scolnik said.

The humidity may have no effect, but researchers said being calmed and comforted by a parent might help -- an assessment shared by Greer.

"Once I got him in my arms, I guess, you know, closer contact, he seemed a lot better," he said.

About 5 percent of children will get croup at least once. It's usually not serious, though 1 percent do end up hospitalized.