An alcohol rub, also known as a hand sanitizer or healthcare personnel hand wash is used as a supplement or alternative to hand washing with soap and water. The active ingredient in alcohol rubs may be isopropanol, ethanol, or (in Europe) propanol. A variety of preparations are available, including gels, foam and liquid solutions. Hand sanitizers containing alcohol are more effective at killing germs than soaps and do not dry out hands as much as soaps.
Alcohol concentration must be above 60% for alcohol rubs to be effective in killing microbes. Researchers at East Tennessee State University found that products with alcohol concentrations as low as 40% are available in American stores.  The optimum alcohol concentration to kill germs is 70 to 95 %. Alcohol gels containing 62 v/v % alcohol are less effective germ killers than alcohol rubs containing at least 70 wt/wt % alcohol.    Alcohol rubs containing two different germ killers (i.e. alcohol and benzalkonium chloride) are significantly more effective than alcohol alone.  Most alcohol rub formulations include a moisturizer to keep hands from drying out.
Alcohol rubs kill many different kinds of bacteria, including antibiotic resistant bacteria and TB bacteria. Alcohol rubs inactivate many different kinds of viruses, including the flu virus and the common cold virus. Alcohol rubs also kill fungus.
Not all pathogens are equally susceptible. Certain bacteria, especially the spore-forming gram positives (e.g. Clostridium difficile) are relatively resistant and remain biologically viable. During the Anthrax attacks on the United States Postal Service, authorities warned that alcohol hand rubs would not kill anthrax spores. In environments with high lipids or protein waste (such as food processing), the use of alcohol hand rubs alone may not be sufficient to ensure proper hand hygiene.
Alcohol gel can catch fire, producing a dim blue flame. This is due to the flammable alcohol in the gel. Some hand sanitizer gels may not produce this effect due to a high concentration of water or moisturizing agents.
There have been numerous, but rare, instances where alcohol hand gels have been implicated in starting fires, including a case where static electricity ignited the gel. To minimize the risk of fire, users are instructed to rub their hands until dry, which indicates that the flammable alcohol has evaporated. 
It has been also noted that if ingested it can cause alcohol poisoning in small children. In the US alone, there have been more than 12,000 cases of child-related alcohol-poisoning directly attributed to hand sanitizer products. 
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