Hand sanitizer, available as a liquid, gel, or foam, kills viruses, bacteria, and other microorganisms on the hands. While widely used and often perceived as highly effective, it does not eliminate all types of germs. This overlooks specific limitations in its germ-killing capabilities.
The Science Behind Hand Sanitizer
Most hand sanitizers use alcohols, such as ethanol or isopropanol, as their primary active ingredients. These alcohols denature proteins essential for a germ’s structure and function. Alcohol also dissolves the protective lipid membranes surrounding many bacteria and enveloped viruses.
This dual action causes germ cells to lose integrity, dehydrate, and die. Effective hand sanitizers require an alcohol concentration between 60% and 95%. Lower alcohol concentrations may only reduce germ growth rather than killing them.
Germs That Resist Hand Sanitizer
Alcohol-based hand sanitizers are not universally potent against all microbes. Some germs are inherently resistant due to their biological structure. Non-enveloped viruses, like norovirus and rhinovirus (common cold), lack the outer lipid membrane alcohol targets. Alcohol cannot penetrate their tough protein capsid, making hand sanitizer ineffective.
Spore-forming bacteria, notably Clostridioides difficile (C. diff), are another category of resistant pathogens. C. diff forms highly resilient spores with a distinct cellular envelope and dehydrated core, allowing survival in harsh conditions and resistance to alcohol inactivation. Eliminating these spores requires physical removal, not chemical destruction. Some bacteria, like certain Vancomycin-resistant Enterococci (VRE) strains, also show increasing alcohol tolerance in healthcare settings, possibly due to genetic adaptations.
Factors That Reduce Effectiveness
Beyond inherent germ resistance, several external factors diminish hand sanitizer’s effectiveness. Visible dirt or grease on hands creates a physical barrier, preventing alcohol contact with germs. Hand sanitizers inactivate microbes; they do not physically remove debris.
Using insufficient sanitizer to cover all hand surfaces compromises efficacy. Failing to rub hands together long enough (20-30 seconds until dry) prevents adequate contact time for alcohol to work. Sanitizers with less than 60% alcohol are not strong enough to effectively kill many germs. If sanitizer evaporates too quickly before sufficient contact time, its germ-killing potential is reduced.
When Handwashing is Best
Given hand sanitizer’s limitations, washing hands with soap and water remains the most effective method for removing all types of germs and chemicals. Handwashing physically removes pathogens, dirt, and grease from skin, rather than merely inactivating them. This physical removal is especially important where hand sanitizer falls short.
Handwashing is recommended in several situations:
- When hands are visibly dirty or greasy (e.g., after outdoor activities or handling food).
- After using the restroom.
- Before eating or preparing food.
- After contact with individuals suffering from diarrheal illnesses (e.g., norovirus or C. diff).
- After blowing your nose, coughing, or sneezing.
- After handling animals, animal waste, or garbage.
While hand sanitizer is a convenient alternative when soap and water are unavailable, it is not a perfect substitute for thorough handwashing.