Think hand sanitizers will keep you safe from the flu this winter?  Think again.  The FDA says they don’t, and is warning the makers of Purell to stop making such claims.

In a letter sent to the company this month, the FDA says it is “not aware of any adequate and well-controlled studies” that prove that hand sanitizers prevent infection from viruses like flu, ebola, MRSA, or norovirus. It also criticized the company for claiming on its website that Purell products reduce “student absenteeism” by 51%.

Purell’s parent company GOJO says it’s taking “immediate action” and is already updating its website.