You'll find the portable versions in grocery stores and drug stores, and large dispensers are increasingly found in public places. But are hand sanitizing gels more effective than hand washing? And how accurate are the claims that these gels can kill 99% of viruses and bacteria found on our skin?
The FDA recommends hand washing with soap and water - with hand sanitizer only as an adjunct. The CDC recommends a high quality hand sanitizer gel if hands are not soiled, because proteins and fats (or any soiling of hands) can prevent effectiveness of the gels which can't cut through that grime.
The gel manufacturer's test results which claim to kill 99% of bacteria (often tests are carried out on inanimate surfaces) may not be accurate for skin. And the amount and type of viruses killed are not certain either. Recent reports suggest certain types of hand sanitizers may be effective in reducing numbers of H1N1 virus, and a 2008 study of a blend of an ethanol-based sanitizer with other ingredients showed improved inactivation of enteric viruses known to cause food-related illnesses (Macinga et al., Appl Environ Microbiol). However, viruses and bacteria are resilient and not all hand sanitizers will kill all types of viruses or bacteria.
The concensus advice appears to be: wash your hands with soap and water if you can first - because clean hands respond better to hand sanitizers. And if you're purchasing a hand sanitizer for personal use, make sure it contains 60-90 percent minimum alcohol concentration (ie: ethanol, isopropyl alcohol), which health officials deem necessary to kill most harmful bacteria and viruses (Emerging Infectious Diseases 2006).
But since we know not everything will be killed - keep your hands away from your mouth and mucus membranes like your eyes, where harmful germs can enter your body. The CDC states that influenza virus is destroyed by heat (167-212°F [75-100°C], but in addition several chemical germicides, including chlorine, hydrogen peroxide, detergents (soap), iodophors (iodine-based antiseptics), and alcohols are effective against human influenza viruses if used in proper concentration for a sufficient length of time. The key part here regarding alcohols (the most common active ingredient in hand sanitizing gels) is PROPER CONCENTRATION for a SUFFICIENT LENGTH OF TIME.
The Mayo Clinic has a great website outlining proper handwashing techniques, and proper use of hand sanitizer gels (http://www.mayoclinic.com/health/hand-washing/HQ00407). The key for the hand gels is that they should cover the entire surface of the hand and stay on the hand for 25 seconds or until hands are dry.
Some studies also suggest that hand sanitizers can kill the good flora living on our skin, however studies are ongoing and currently there seems to be no concensus about whether this would have a harmful effect on health. Healthy bacteria live in many areas of our body, including the skin and gastrointestinal tract (a great lay article about this is here: http://www.nytimes.com/2008/05/23/science/23gene.html).
Another reference from Dr. Sanjay Gupta: