And since hand sanitizers became so widely used after the swine flu arrived, the study essentially lost its "control" group.
But while these findings don't mean hand sanitizers are useless against asthma, there's also little evidence that their use in schools benefits kids.
"Hand washing is probably best, and it's cheapest," Gerald said.
"It's unclear right now," she added, "whether hand sanitizers are a worthwhile investment for schools."
Gerald thinks studies should continue to look at the question, though. One reason is the fact that some schools are already using hand sanitizers, sometimes as a replacement for soap and water.
"I think we need to know how they can be used most effectively," Gerald said.
Many parents may be sending their kids off to school with a little bottle of hand sanitizer. That may or may not be helpful.
Gerald suggested teaching your kids about good hygiene in general, whether they have asthma or not. That includes hand washing, "covering up" when you cough, and keeping your fingers away from your mouth and eyes, she said.
GOJO said it "hopes the researchers will continue to study the effect of hand hygiene to reduce asthma rates with future scientific studies conducted in real world settings."
None of the researchers reports any connection to the company, but one of Gerald's colleagues on the work has ties to drug companies that make asthma medication.
(Additional reporting by Ivan Oransky)
SOURCE: http://bit.ly/UDGV5L Journal of Allergy and Clinical Immunology, online October 15, 2012.