Final answer:
Hand sanitizers are ineffective on dirty or greasy hands because contaminants can shield germs from the active ingredients and prevent proper application.
Step-by-step explanation:
Waterless hand sanitizers and antiseptics will not work on dirty or greasy hands.Alcohol-based hand sanitizers, which typically contain 60% to 80% isopropanol or ethanol, are effective in killing bacteria and viruses on clean surfaces. However, their effectiveness is greatly reduced when hands are heavily soiled or greasy. Substances like dirt, oil, or certain food residues can physically shield microorganisms from the sanitizer's active ingredients. Moreover, these contaminants may also hinder the even distribution of the sanitizer on the hands, resulting in poor disinfection. Therefore, it's important to clean one's hands with water and soap prior to applying hand sanitizer for maximum effectiveness. Overuse of antimicrobial products can lead to increased risk of infection by disrupting the skin's natural defenses and potentially leading to antibiotic resistance.
In waterless hand sanitizers and antiseptics, the active ingredients like isopropanol or ethanol are effective in killing bacteria and enveloped viruses. However, they may not be effective against non-enveloped viruses such as norovirus and rotavirus. These non-enveloped viruses have a more resistant outer shell that is not easily penetrated by hand sanitizers or antiseptics. Therefore, it is important to wash hands with soap and water to effectively remove and kill these types of viruses.