Aesthetic Dermatology Update

Hand washing and hand sanitizer on the skin and COVID-19 infection risk


As we deal with the effects of the COVID-19 pandemic, hand washing and the use of hand sanitizers have been key for infection prevention. With drier, colder weather in many of the communities initially affected by COVID-19, skin was already prone to dryness and a skin barrier compromised, and hand eczema was more prevalent because of these factors alone. This article explores the effects of hand washing and hand sanitizer on skin and how this prevents infection, and explores methods to promote skin health while maintaining the maximum possible degree of infection prevention.

Dr. Naissan O. Wesley, a dermatologist who practices in Beverly Hills, Calif.

Dr. Naissan O. Wesley

With many viruses, including coronavirus, the virus is a self-assembled nanoparticle in which the most vulnerable structure is the outer lipid bilayer. Soaps dissolve the lipid membrane and the virus breaks apart, inactivating it; they are also alkaline surfactants that pick up particles – including dirt, bacteria, and viruses – which are removed from the surface of the skin when the soaps are rinsed off. In the process of washing, the alkalinity of the soap (pH approximately 9-10), compared with the normal outer skin pH of approximately 5.5 or lower, also can affect the skin barrier as well as the resident skin microflora. In a study by Lambers et al., it was found that an acid skin pH (4-4.5) keeps the resident bacterial flora attached to the skin, whereas an alkaline pH (8-9) promotes the dispersal from the skin in assessments of the volar forearm.

With regard to the effectiveness of hand washing against viruses, the length of time spent hand washing has been shown to have an impact on influenza-like illness. In a recent study of 2,082 participants by Bin Abdulrahman et al., those who spent only 5-10 seconds hand washing with soap and hand rubbing were at a higher risk of more frequent influenza-like illness (odds ratio, 1.37; 95% confidence interval, 1.08-1.75), compared with those who washed their hands for 15 seconds or longer. Moreover, hand washing with soap and rubbing after shaking hands was found to be an independent protective factor against frequent influenza-like illness (adjusted OR, 0.59; 95% confidence interval, 0.37-0.94). Previous studies on the impact of hand washing on bacterial and parasitic illnesses also found similar results: Hand washing for 15-20 seconds or longer reduces infection.

Alcohol, long known as a disinfectant, has been recommended for disinfecting the hands since the late 1800s. Most alcohol-based hand antiseptics contain isopropanol, ethanol, N-propanol, or a combination of two of these products. The antimicrobial activity of alcohols can be attributed to their ability to denature and coagulate proteins, thereby lysing microorganisms’ cells, and disrupting their cellular metabolism. Alcohol solutions containing 60%-95% alcohol are the most effective. Notably, very high concentrations of alcohol are less potent because less water is found in higher concentrations of alcohol and proteins are not denatured easily in the absence of water. Alcohol-based hand sanitizers also often contain humectants, such as glycerin and/or aloe vera, to help prevent skin dryness and replace water content that is stripped by the use of alcohol on the skin surface.

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