Since June, the agency has been expanding its list of hand sanitizers that may be contaminated with deadly methanol alcohol. But on Friday, the FDA announced a new problem. While some hand sanitizers contain the wrong kind of alcohol, others don't have enough of the right kind.

"FDA test results show certain hand sanitizers have concerningly low levels of ethyl alcohol or isopropyl alcohol, which are active ingredients in hand sanitizer products," the FDA wrote. "The agency urges consumers not to use these subpotent products."

The Centers for Disease Control and Prevention (CDC) recommends washing your hands with soap and water for at least 20 seconds as the best hand hygiene method to prevent the spread of disease. Soap and water is more effective than hand sanitizer at killing certain germs, and some people do not use hand sanitizer correctly, either wiping it off too early or not using enough.

However, if soap and water are not available, the CDC recommends using a hand sanitizer that contains at least 60 percent ethanol alcohol.

"Many studies have found that sanitizers with an alcohol concentration between 60–95% are more effective at killing germs than those with a lower alcohol concentration or non-alcohol-based hand sanitizers," the CDC explained. "Hand sanitizers without 60-95% alcohol 1) may not work equally well for many types of germs; and 2) merely reduce the growth of germs rather than kill them outright."

The rise in hand sanitizer demand has been driven by attempts to stop the spread of the new coronavirus, so it is important that products actually work.

The FDA flagged the following hand sanitizers for being less effective:

1. dgreen Advanced Sanitizer Alcohol Free
2. dgreen Advanced Hand Sanitizer Antibacterial Gel
3. Biokaab Inc. Hand Sanitizer
4. Biokaab Inc. Hand Sanitizer Gel
5. Clean Humans Hand Sanitizer
6. Medicare Alcohol Antiseptic Topical Solution
7. NeoNatural
8. Datsen Hand Sanitizer
9. Alcohol Antiseptic 62% Hand Sanitizer
10. Bernal Hand Sanitizer
11. Inflatables LLC Alcohol Antiseptic 65% Hand Sanitizer and Alcohol Antiseptic 70% Hand Sanitizer

In addition to the subpotent hand sanitizers, the FDA continues to warn against hand sanitizers that contain methanol, or wood alcohol, which is toxic when absorbed through the skin and can be deadly when swallowed. There have been reports of people going blind, damaging their hearts or nervous systems, being hospitalized and even dying because of exposure to these toxic hand sanitizers, the agency said in a news release. One of the deaths was associated with Blumen Hand Sanitizer, which is distributed by 4e North America and manufactured by 4E Global in Mexico. The company has recalled an expanded list of products.

"Practicing good hand hygiene, which includes using alcohol-based hand sanitizer if soap and water are not readily available, is an important public health tool for all Americans to employ. Consumers must also be vigilant about which hand sanitizers they use, and for their health and safety we urge consumers to immediately stop using all hand sanitizers on the FDA's list of dangerous hand sanitizer products," FDA Commissioner Dr. Stephen M. Hahn said in the press release. "We remain extremely concerned about the potential serious risks of alcohol-based hand sanitizers containing methanol. Producing, importing and distributing toxic hand sanitizers poses a serious threat to the public and will not be tolerated. The FDA will take additional action as necessary and will continue to provide the latest information on this issue for the health and safety of consumers."

There are now 115 hand sanitizers on the agency's "do-not-use list," mostly manufactured in Mexico, CNN reported. As such, the FDA has issued import alerts to stop the products from entering the U.S.

It also sent a warning letter to one of the companies involved, Eskbiochem S.A. de C.V., for poor manufacturing practices, distributing hand sanitizers made at a facility that has undeclared methanol and falsely claiming its products are FDA approved.