When is it appropriate to use an alcohol-based hand sanitizer?

Using an alcohol-based hand sanitizer is appropriate when no visual contamination is present because such sanitizers are effective in reducing the number of germs in the absence of visible dirt or debris. They work by killing most types of germs (bacteria and viruses) on the skin, provided that the hands are not excessively soiled. If hands are visibly dirty or greasy, handwashing with soap and water is recommended as it is more effective at removing dirt, organic material, and certain germs that hand sanitizers may not effectively eliminate.

In situations where hygiene is critical, such as before preparing or consuming food, alcohol-based hand sanitizers are beneficial only when hands are clean initially. After contact with animals or their environments, washing hands with soap and water is preferred due to the potential presence of biological contaminants that sanitizers alone might not address.