Parents who warn their kids not to eat dirty snow (especially the yellow variety) are left wondering whether to stop them from tasting the new-fallen stuff, too, because of Pseudomonas syringae, bacteria that can cause diseases in bean and tomato plants.
But experts say there's no need to banish snow-eating along with dodgeball, unchaperoned trick-or-treating and riding a bike without a helmet.
"It's a very ubiquitous bacteria that's everywhere," says Dr. Penelope Dennehy, a member of the American Academy of Pediatrics' committee on infectious diseases. "Basically, none of the food we eat is sterile. We eat bacteria all the time."
Children practically bathe in bacteria when they go to the playground, and Dennehy says they won't get anything from snow that they wouldn't get from dirt.
"We eat stuff that's covered with bacteria all the time, and for the most part it's killed in the stomach," says Dr. Joel Forman, a member of the pediatric academy's committee on environmental health. "Your stomach is a fantastic barrier against invasive bacteria because it's a very acidic environment."
There are exceptions. "Tiny kids on formula a lot of times don't have the acid in their stomachs," making them more vulnerable to bacteria in general, says Dr. Lynnette Mazur, a professor of pediatrics at the University of Texas Medical School. Also, Forman and Mazur say that Pseudomonas can be a threat to people with cystic fibrosis.
The study, published last week in the journal Science, didn't examine the effects on people. And experts say without further information, it is impossible to say what the bacteria could do to a child who eats extraordinary amounts.
"I can say that I'm not aware of any clinical reports of children becoming ill from eating snow. And I looked," Forman says.
In any case, because of ordinary air pollution in snow, it's probably wise not to eat a lot of the stuff, pediatricians say. For parents in search of guidance, Mazur offers this: Licking a little snow off a glove is probably OK. "A meal of snow" is not.
Some parents say they are not going to worry about their kids eating snow that looks clean.
"My snow-eating concerns are generally more of the dirt-urine variety," says Kristin Lang, 37, of Maplewood, N.J., whose 2-year-old son Charlie has swallowed his share of snow.
"When I heard bacteria, at first I went 'eew,"' says Tricia Sweeney, a mother of three in Cornwall-on-Hudson, N.Y. But as long as the kids eat snow as it's falling, "I think it's OK. I tell them not to eat it if it's on the ground."