Show Me the Science - How to Wash Your Hands

Why? Because hands could become recontaminated if placed in a basin of standing water that has been contaminated through previous use, clean running water should be used ¹. However, washing with non-potable water when necessary may still improve health ^{2, 3}. The temperature of the water does not appear to affect microbe removal; however, warmer water may cause more skin irritation and is more environmentally costly ^4-6.

Turning off the faucet after wetting hands saves water, and there are few data to prove whether significant numbers of germs are transferred between hands and the faucet.

Using soap to wash hands is more effective than using water alone because the surfactants in soap lift soil and microbes from skin, and people tend to scrub hands more thoroughly when using soap, which further removes germs ^2,3,7,8.

References

1. Palit A, Batabyal P, Kanungo S, Sur D. In-house contamination of potable water in urban slum of Kolkata, India: a possible transmission route of diarrhea. Water Sci Technol. 2012;66(2):299-303.
2. Luby SP, Agboatwalla M, Feikin DR, Painter J, Billhimer W, Altaf A, Hoekstra RM. Effect of handwashing on child health: a randomised controlled trial. Lancet. 2005;366:225-33.
3. Luby SP, Halder AK, Huda T, Unicomb L, Johnston RB. The effect of handwashing at recommended times with water alone and with soap on child diarrhea in rural Bangladesh: an observational study. PLoS Med. 2011 Jun;8(6):e1001052.
4. Carrico AR, Spoden M, Wallston KA, Vandenbergh MP. The environmental cost of misinformation: why the recommendation to use elevated temperatures for handwashing is problematic. Int J Consum Stud. 2013 Jul 1;37(4):433-441.
5. Laestadius JG, Dimberg L. Hot water for handwashing–where is the proof? J Occup Environ Med. 2005 Apr;47(4):434-5.
6. Michaels B, Gangar V, Schultz A, Arenas M, Curiale M, Ayers T, Paulson D. Water temperature as a factor in handwashing efficacy. Food Service Technology. 2002;2:139-49.
7. Burton M, Cobb E, Donachie P, Judah G, Curtis V, Schmidt WP. The effect of handwashing with water or soap on bacterial contamination of hands. Int J Environ Res Public Health. 2011 Jan;8(1):97-104.
8. Todd ECD, Michaels BS, Holah J, Smith D, Grieg JD, Bartleson CA. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 10. Alcohol-based antiseptics for hand disinfection and a comparison of their effectiveness with soaps. J Food Prot. 2010 Nov;73(11):2128-40.
9. Luby SP, Agboatwalla M, Painter J, Altaf A, Billhimer WL, Hoekstra RM. Effect of intensive handwashing promotion on childhood diarrhea in high-risk communities in Pakistan: a randomized controlled trial. JAMA. 2004 Jun 2;291(21):2547-54.
10. Larson EL, Lin SX, Gomez-Pichardo C, Della-Latta P. Effect of antibacterial home cleaning and handwashing products on infectious disease symptoms: a randomized, double-blind trial. Ann Intern Med. 2004 Mar 2;140(5):321-9.

Why? Lathering and scrubbing hands creates friction, which helps lift dirt, grease, and microbes from skin.  Microbes are present on all surfaces of the hand, often in particularly high concentration under the nails, so the entire hand should be scrubbed ^1-5.

References

1. Gordin FM, Schultz ME, Huber R, Zubairi S, Stock F, Kariyil J. A cluster of hemodialysis-related bacteremia linked to artificial fingernails. Infect Control Hosp Epidemiol. 2007 Jun;28(6):743-4.
2. Hoque BA. Handwashing practices and challenges in Bangladesh. Int J Environ Health Res. 2003 Jun;13 Suppl 1:S81-7.
3. Lin CM, Wu FM, Kim HK, Doyle MP, Michael BS, Williams LK. A comparison of hand washing techniques to remove Escherichia coli and caliciviruses under natural or artificial fingernails. J Food Prot. 2003 Dec;66(12):2296-301.
4. McGinley KJ, Larson EL, Leyden JJ. Composition and density of microflora in the subungual space of the hand. J Clin Microbiol. 1988 May;26(5): 950–953.
5. Todd EC, Michaels BS, Smith D, Greig JD, Bartleson CA. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 9. Washing and drying of hands to reduce microbial contamination. J Food Prot. 2010 Oct;73(10):1937-55.

Why? Determining the optimal length of time for handwashing is difficult because few studies about the health impacts of altering handwashing times have been done. Of those that exist, nearly all have measured reductions in overall numbers of microbes, only a small proportion of which can cause illness, and have not measured impacts on health. Solely reducing numbers of microbes on hands is not necessarily linked to better health ¹. The optimal length of time for handwashing is also likely to depend on many factors, including the type and amount of soil on the hands and the setting of the person washing hands.  For example, surgeons are likely to come into contact with disease-causing germs and risk spreading serious infections to vulnerable patients, so they may need to wash hands longer than a woman before she prepares her own lunch at home. Nonetheless, evidence suggests that washing hands for about 15-30 seconds removes more germs from hands than washing for shorter periods ^2-4.

Accordingly, many countries and global organizations have adopted recommendations to wash hands for about 20 seconds (some recommend an additional 20-30 seconds for drying):

• Canada. The Benefits of Hand Washing
• New Zealand. Step-by-Step Guide to Hand Washing
• The Global Public-Private Partnership for Handwashing. Why Handwashing?
• World Health Organization. Guidelines on Hygiene in Health Care: A Summary[PDF – 64 pages]

References

1. Luby SP, Agboatwalla M, Billhimer W, Hoekstra RM. Field trial of a low cost method to evaluate hand cleanliness. Trop Med Int Health. 2007 Jun;12(6):765-71
2. Fuls JL, Rodgers ND, Fischler GE, Howard JM, Patel M, Weidner PL, Duran MH. Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions. Appl Environ Microbiol. 2008 Jun;74(12):3739-44.
3. Jensen D, Schaffner D, Danyluk M, Harris L. Efficacy of handwashing duration and drying methods. Int Assn Food Prot. 2012 July.
4. Todd EC, Michaels BS, Smith D, Greig JD, Bartleson CA. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 9. Washing and drying of hands to reduce microbial contamination. J Food Prot. 2010 Oct;73(10):1937-55.

Why? Soap and friction help lift dirt, grease, and microbes—including disease-causing germs—from skin so they can then be rinsed off of hands. Rinsing the soap away also minimizes skin irritation ¹. Because hands could become recontaminated if rinsed in a basin of standing water that has been contaminated through previous use, clean running water should be used ^2,3  While some recommendations include using a paper towel to turn off the faucet after hands have been rinsed, this practice leads to increased use of water and paper towels, and there are no studies to show that it improves health.

References

1. Todd EC, Michaels BS, Smith D, Greig JD, Bartleson CA. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 9. Washing and drying of hands to reduce microbial contamination. J Food Prot. 2010 Oct;73(10):1937-55.
2. Palit A, Batabyal P, Kanungo S, Sur D. In-house contamination of potable water in urban slum of Kolkata, India: a possible transmission route of diarrhea. Water Sci Technol. 2012; 66(2):299-303.
3. Hoque BA. Handwashing practices and challenges in Bangladesh. Int J Environ Health Res. 2003 Jun;13 Suppl 1:S81-7.

Why? Germs can be transferred more easily to and from wet hands; therefore, hands should be dried after washing. ^{1, 2} However, the best way to dry hands remains unclear because few studies about hand drying exist, and the results of these studies conflict. Additionally, most of these studies compare overall concentrations of microbes, not just disease-causing germs, on hands following different hand-drying methods. It has not been shown that removing microbes from hands is linked to better health ³. Nonetheless, studies suggest that using a clean towel or air drying hands are best ^4-6.

References

1. Patrick DR, Findon G, Miller TE. Residual moisture determines the level of touch-contact-associated bacterial transfer following hand washing. Epidemiol Infect. 1997 Dec;119(3):319-25.
2. Todd EC, Michaels BS, Smith D, Greig JD, Bartleson CA. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 9. Washing and drying of hands to reduce microbial contamination. J Food Prot. 2010 Oct;73(10):1937-55.
3. Luby SP, Agboatwalla M, Billhimer W, Hoekstra RM. Field trial of a low cost method to evaluate hand cleanliness. Trop Med Int Health. 2007 Jun;12(6):765-71
4. Gustafson DR, Vetter EA, Larson DR, Ilstrup DM, Maker MD, Thompson RL, Cockerill FR 3rd. Effects of 4 hand-drying methods for removing bacteria from washed hands: a randomized trial. Mayo Clin Proc. 2000 Jul;75(7):705-8.
5. Huang C, Ma W, Stack S. The hygienic efficacy of different hand-drying methods: a review of the evidence. Mayo Clin Proc. 2012 Aug;87(8):791-8.
6. Jensen D, Schaffner D, Danyluk M, Harris L. Efficacy of handwashing duration and drying methods. Int Assn Food Prot Annual Meeting. 2012 July 22-25.