Yale University researchers are on your mom’s side when it comes to fighting a cold: Put on a sweater.

The immune system doesn’t combat cold viruses as well at lower temperatures, according to an early study in mice published Monday in the Proceedings of the National Academy of Sciences. Doctors have understood for decades that temperature affects the way cold viruses reproduce. Akiko Iwasaki, a Yale professor of immunobiology who led Monday’s study, now has research, as well as motherly intuition, to bolster the case for staying warm that she makes to her kids.

“Fashion goes out the window when it comes to protecting my children,” Iwasaki said in an interview. “I bundle them up and they don’t like it. As a mother and as a scientist it’s my duty to do that.”

Researchers at Yale in New Haven, Conn., introduced rhinovirus, the prime cause of the common cold, and monitored the immune response in cells from the airways of mice incubated at core human body temperature and at a lower temperature.

They found that low temperatures suppressed the cells’ ability to detect viruses as well as their mechanism for alerting the immune system, allowing viruses more freedom to replicate.

In cells that had a genetically compromised immune response, the virus thrived equally in warm and cool environments, according to the study.

“The virus can replicate better because the alarm signal is turned off,” Iwasaki said.

“If you remove the sensor or the signal then the virus can replicate at even the higher temperature.”

The most common human illness, colds are the main reason that children miss school and adults miss work, according to the Centers for Disease Control and Prevention.

While colds generally run their course in seven to 10 days, more seriously they can lead to fatal asthma flare-ups and hospitalization of children with the chronic lung disease.

Iwasaki will next try the experiment with human cells.