Hydroalcoholic product: the consequences on our hands.

The hydroalcoholic product is a rinse-free, quick-drying solution with bactericidal, fungicidal, and virucidal activity. It is primarily composed of an alcohol (ethanol or isopropanol) with a nominal content of at least 60% to ensure disinfectant properties, an emollient (glycerol, aloe vera, etc.) to prevent skin dryness, and sometimes an antiseptic (hydrogen peroxide, triclosan, chlorhexidine, etc.). Firstly, unlike soap which cleans, the hydroalcoholic solution is not effective on dirt, whether visible or not (pollution particles, etc.). Therefore, for the hydroalcoholic gel to fulfil its functions, one must have relatively clean hands, that is, free from chemical and organic soiling, otherwise the microbes will be camouflaged in the dirt present on our skin and will act as a protective film between the alcohol molecules and the microorganisms. The effects of the alcohol will then be diminished.

Similar to soap, disinfectant products also work by attacking the membrane of microorganisms. The difference is that the alcohol molecules in solution will target and denature the membrane proteins of the microorganisms, which are essential to their activity, but also inhibit the synthesis of their nucleic acids and proteins. The alcohol will effectively alter the spatial organisation of the proteins, causing them to lose their biological properties. Another difference is that hand sanitiser is able to kill the microorganisms rather than remove them as soap does through friction and rinsing with water. Alcohols thus prove effective against most bacteria, enveloped viruses, yeasts, moulds and naked viruses (those lacking a viral envelope). However, its ineffectiveness against spores has been noted. Nevertheless, studies comparing it to soap have shown that hand sanitiser is effective in reducing the presence of the flu virus on hands, but traditional washing with soap and water is even more so. Therefore, even though hand sanitiser is ideal and convenient for outdoor use, remember to wash your hands with soap and water as often as possible throughout the day.

For the product to be effective, it is necessary to adopt the correct techniques to use it properly. First rule : Always apply your antiseptic solution to dry, unbroken, undamaged hands without visible dirt. Indeed, if you apply it to wet hands, the product will be diluted and its effectiveness reduced. Similarly, the alcohol contained in the solution is deactivated by the presence of too much oil on the skin. Therefore, apply a sufficient dose of lotion in the palm of your hand (about 3 mL). Then rub vigorously for at least 30 seconds until the hydroalcoholic solution has completely evaporated (dry hands) and the emollient has fully penetrated (non-sticky hands). Remember to thoroughly rub the back and palms of your hands, the tips of your fingers, under the nails, the spaces between your fingers, as well as your wrists. Remember : The hydroalcoholic product has been designed solely for hand disinfection. Therefore, it is advisable to avoid any contact with the mucous membranes.

Hand sanitiser gel is capable of eliminating most germs. However, in the process, the alcohol also disrupts the skin's natural hydrolipidic film, leading to dryness, cracks, irritation, tightness, and vulnerability to external aggressions. Daily and frequent use of hand sanitiser gel can also alter the microbiome present on the skin's surface. Indeed, when we use the sanitising solution, we not only destroy the pathogenic organisms of the transient flora that can cause serious diseases, but we also reduce the resident flora of the epidermis which contributes to our immune defences. But don't panic, it quickly reforms. However, the same observation is made with soap. Moreover, intensive and excessive use of hand sanitiser gel, like with soap, can cause eczema and atopic dermatitis, weakening the epidermis and exposing it to exogenous infectious agents.

Hand sanitisers prove to be indispensable in high-risk situations, for instance during an epidemic. However, intensive and frequent use can cause discomfort to the skin. Much like soap, the hand sanitiser will remove the skin's hydrolipidic film and destroy the resident flora, both of which are responsible for protecting the skin from external aggressions. To minimise damage and maintain the epidermis, opt for a hand sanitiser concentrated in emollient active ingredients (glycerine, aloe vera, etc...) and above all, remember to consistently hydrate your hands daily with a dab of nourishing care.

• BIRCH C. & al. Efficacy of soap and water and alcohol-based hand-rub preparations against live H1N1 influenza virus on the hands of human volunteers. Clinical Infectious Diseases (2009).

• CALVO-SOTELO A.E. & al. Comparative study of presurgical hand hygiene with hydroalcoholic solution versus traditional presurgical hand hygiene. Enfermeria Clinica (2017).

• ITOHA Y. & al. Situations leading to reduced effectiveness of current hand hygiene against infectious mucus from influenza virus-infected patients. American Society for Microbiology (2019).