Why is hand sanitizer not considered a substitute for handwashing?

Hand sanitizer is not considered a substitute for handwashing because it may not effectively remove all pathogens and physical dirt. While hand sanitizers can kill many types of germs, they are not effective against certain types of pathogens, such as some viruses and bacteria that are present in high numbers, particularly if hands are visibly dirty or greasy. Washing hands with soap and water not only helps to eliminate germs but also physically removes dirt, debris, and other contaminants from the skin's surface. This thorough cleaning action is something that hand sanitizers cannot achieve, making proper handwashing the preferred method for ensuring hand hygiene in most circumstances.