Soap or alcohol‐based products? The effect of hand hygiene on skin characteristics during the COVID‐19 pandemic

Abstract

Background

Different strategies for hand skin hygiene have been used to prevent the spread of SARS‐CoV‐2. However, frequent hand sanitization has been associated with skin damage. The present study aimed to evaluate hand hygiene habits during the COVID‐19 pandemic and the effect of the repetitive use of soap or alcohol‐based products on skin characteristics.

Methods

We conducted a survey regards hand hygiene habits acquired during the COVID‐19 pandemic. Also, we performed cutometry in a cohort of individuals who cleansed their volar forearms every 30 min, during 4 h, using soap or alcohol‐based products.

Results

We received 138 responses from people with medium‐high educational level who reported a 2.5‐time increase in the frequency of hand cleansing (p < 0.0001) that resulted in skin damage. An in vivo analysis of skin moisture and elasticity was also performed among 19 health workers and students. In general, skin moisture decreased with every cleansing, mainly after 2 h of washing with soap (p < 0.01), while skin elasticity only reduced after 4 h of treatment (p < 0.05). Alcohol‐based solution or alcohol‐based gel (70% ethanol, both) did not affect skin moisture or elasticity during testing.

Conclusion

It is known that the excessive use of soap or alcohol‐based products causes dermatological issues. The present study demonstrates that non‐medicated soap significantly affects skin moisture and elasticity, probably because the soap removes the hydrolipidic protective barrier, favoring transepidermal water loss, where the lack of the appropriate stratum corneum hydration also affects skin elasticity, mainly associated with changes in epidermal structure.

INTRODUCTION

Frequent hand cleansing is the main recommendation to prevent the transmission and spread of SARS-CoV-2 (a virus that causes COVID-19 disease). Hand cleansing is typically accomplished by rubbing the hands with an alcohol-based disinfectant or washing them with soap and water. Repeated cleansing may have adverse effects on the skin, such as redness, dryness, erythematous scaly patches, and skin thickening. Patients with risk factors, such as a history of atopic dermatitis, may experience more skin side effects. In healthcare workers, repeated hand cleansing is often associated with dermatitis, while occupational contact dermatitis can affect the quality of life and the activities of different types of workers. During the COVID-19 pandemic, the prevalence of occupational skin dermatitis increased in the general population.

Alcohol-based products have a broad spectrum of action against microorganisms and viruses. Still their repeated use can damage the skin by denaturing proteins and dissolving lipids from suprabasal layers of the epidermis because alcohols are small amphiphilic molecules that can affect the structure of the cell membrane of living cells. In vitro studies have shown that alcohol treatment causes changes in keratinocyte metabolic activity, inflammatory cytokine release, and lytic enzymatic activity. Traditional soaps are often alkaline, containing anionic surfactants, chelating agents (i.e., ethylenediaminetetraacetic acid), and other ingredients such as moisturizers, emollients, and fragrances, all of them involved in skin irritation when absorbed. Surfactants, which reduce the skin's surface tension and remove dirt in an emulsified form, are the main components of these cleansing agents. They remove microorganisms, viruses, sweat, and sebum from the skin. Exposing the skin to soap is associated with changes in the morphology of corneocytes (dead keratinocytes filled primarily with keratin) and inflammatory cytokine release. Intrinsic and extrinsic factors can thus affect skin biophysical properties such as moisture, pigmentation, and elasticity; and the alteration of stratum corneum properties induces changes in the chemical and biomechanical properties of the skin surface, as well as its physical appearance.

The complex structure of the human epidermis protects the body from entering of external agents such as microorganisms, viruses, and water-soluble substances and prevents water loss. The different epidermic layers are formed by keratinocytes, which proliferate only in the basal layer and gradually differentiate toward the upper layers until they reach the stratum corneum, composed of corneocytes. During the formation of the corneal layer, cells release the lipid content of lamellar granules into the extracellular space, resulting in the formation of the lipid lamellar matrix, which forms a kind of “mortar,” a type of dynamic cement, into which the corneocytes become embedded. Together with keratin proteins, this constitutes a “brick and mortar” structure. The stratum corneum's proteins and lipids give the epidermis most of its elastic properties and allow it to perform its barrier function.

The present study aimed to evaluate the effect of frequent hand cleansing on the biophysical properties of the skin. A survey was conducted among the general population to analyze changes in hand hygiene habits during the pandemic. Then, a pilot trial was used to evaluate the in vivo effects of frequent forearm cleansing using soap, 75% alcohol-based solution, or 75% alcohol-based gel.

MATERIALS AND METHODS

An internet survey entitled “Hand hygiene habits acquired during the COVID-19 pandemic” was conducted using the Google application. Before the final release of the survey, the questionnaire was tested among a pilot group of people. After processing the feedback, reviewing, and analyzing the questions and answers, the final survey was prepared and distributed via social media. Personal data were handled with confidentiality.

A prospective, analytical, open, and self-controlled study was conducted from November 2021 to January 2022. Adult men and women without any history of atopic dermatitis, allergies, or adverse reactions to the products or raw materials used in the study were enrolled. Patients without skin lesions in the forearm provided written informed consent for their participation in this non-invasive assay. Subjects were asked to avoid the use of skin care products during the 24 h before the study began and to wear short sleeves during the test. Four similar areas of 2 cm² in both volar forearms, each separated from the others by 4 cm, were designated for the assay. Three areas were selected for the different treatments and the fourth was used as control (skin without treatment), Figure . The evaluated treatments consisted of on-demand washing with anionic non-medicated liquid soap (Gel Kleen) removed with tap water, or with 1 ml alcohol-based solution (AZ, 70% v/v ethanol) or 0.4 g alcohol-based gel (Purell, 70% v/v ethanol, Akron, USA). With the arms extended down, the treatments with the less superficial tension (liquid soap and alcoholic solution) were applied at the distal regions of the forearms, so as to prevent slipping towards the upper zones (control and alcohol-based gel treatments). The subjects spent at least 30 s washing with soap and rubbing the alcohol-based products. The areas washed with soap were dried by patting with paper towels, while the regions containing alcohol-based products were dried by allowing the product to evaporate freely.

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The treatments were applied every 30 min, and measurements were made before (baseline), and after the treatments at 0, 2, and 4 h (1, 5, or 9 applications of every product, respectively), Figure . A Corneometer CM825 (CK electronic GmbH) probe was used to measure skin moisture. The probe was wiped with a dry tissue and 5 measurements were taken in succession. The mean value of each treated site was used for the analysis. Net elasticity (R5), referred to in this study as skin elasticity, was evaluated using a dual MPA 580 cutometer (CK electronic GmbH) with a 2 mm diameter probe. Measurements were carried out in time-strain mode with 10 cycles of 450 mbar of negative pressure during 2 s, followed by a relaxation time for 2 s. The average value of four independent measurements was used for the analysis. Measurements were performed in an isolated room at 18 ± 2°C and 45 ± 5% relative humidity.

Statistical analysis

The survey data were analyzed using descriptive statistics, including mean, standard deviation (SD), range, and frequency. Mann–Whitney test was used to compare the data from the survey regarding the frequency of handwashing before and after the pandemic. Skin moisture and elasticity results were assessed using repeated measures of analysis of variance and Tukey–Kramer multiple comparison test, as well as correlation tests (Pearson's and Spearman's correlation tests for variables with Gaussian distribution). The baseline data were used to show the differences between treatments. Percentages of moisture change, and elasticity were evaluated using the Friedman's test (nonparametric repeated measures ANOVA). Dunn's multiple comparison test was used to analyze the differences with respect to the control and time 0 h. p values ≤0.05 were considered significant.

RESULTS

Changes in hand hygiene habits in the general population during the COVID-19 pandemic and skin side effects. Results from a survey

The survey received 138 responses from a heterogeneous population, where 68.8% were women. The mean age was 39 years (range 18–74 years) and 87.6% had a bachelor degree or were bachelor students. From the total surveyed population, 52.9% had a background of studies in chemistry, biology, or medicine. Before the COVID-19 pandemic, 84% of the respondents used to wash their hands 6.7 ± 4.6 times per day (mean ± SD). During the COVID-19 pandemic, 97% of the respondents increased their hand-washing habits to 14.5 ± 10.3 times per day (mean ± SD), (p < 0.0001). The COVID-19 pandemic not only led to an increase in the number of times people washed their hands, but also to an increase in the frequency with which they did it since 59.4% of the respondents washed their hands more than eight times in 4 h. Of the respondents, 47% washed their hands during working hours, 35% at home (during meal preparation), 20% when using public transportation or performing other non-work-related activities outside their home (i.e., shopping or gym). Regarding the use of hand hygiene products, 79% of used soap, 67% alcohol-based gel, 13% alcohol-based solutions, and 18% other products (sanitizing wipes and alcohol-free products). This shows that each of the respondents used different products to clean their hands. From the surveyed people, 70.3% reported changes in the skin as a result of the high frequency of cleansing, such as dryness (61.5%), irritation (10.1%), itching (6.5%), redness (4.3%), and even skin wounds (7%). According to the survey, the products with the most negative reactions were alcohol-based gel (42.8%), soap (15.2%), and alcohol-based solutions (11.6%).

As a result, from the data obtained through the survey, we performed a moisture and skin elasticity non-invasive trial among a cohort of health workers or health sciences students. Nineteen adult patients with no history of skin disease (4 women and 15 men, mean age 38 years, range 23–62) were enrolled in the trial.

Effect of hand sanitizer products on forearm skin moisture

Skin moisture was measured by corneometry, which evaluates by electric impedance, the water allocated in the suprabasal layers of epidermis. The forearm exhibited slight but significant differences in basal skin moisture between left and right limbs (p < 0.05, Figure  and Table ).

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TABLE 1 Skin moisture and elasticity measurements obtained by cutometry and corneometry, respectively

Treatment, time (Groups, hours)	Skin moisture (A.U)A	Change in moisture from baseline (%)B	Net elasticity (R5)A	Change in elasticity from baseline (%)B
Control
Baseline	39.1 ± 8.9		0.91 ± 0.09
0 h	40.1 ± 9.5*	2.1 ± 2.9	0.92 ± 0.11	0.35 ± 5.35
2 h	39.9 ± 9.4	1.5 ± 4.8	0.94 ± 0.11	2.34 ± 5.40
4 h	39.8 ± 9.6	1.3 ± 4.6	0.94 ± 0.10*	3.40 ± 3.16*
Soap
Baseline	39.6 ± 8.2		0.88 ± 0.12
0 h	38.1 ± 7.8	−4.1 ± 6.5	0.86 ± 0.10	−1.66 ± 7.50
2 h	36.2 ± 7.3***	−10.0 ± 11.3*	0.84 ± 0.10	−4.58 ± 9.64
4 h	35.4 ± 6.9***	−12.3 ± 13.9*	0.82 ± 0.11**	−6.83 ± 10.10
Alcohol- based solution
Baseline	42.3 ± 8.0		0.88 ± 0.09
0 h	41.7 ± 7.0	−1.3 ± 5.4	0.87 ± 0.11	−2.38 ± 8.57
2 h	40.5 ± 7.0	−4.7 ± 9.1	0.86 ± 0.08	−3.13 ± 12.69
4 h	39.7 ± 6.0	−6.4 ± 11.2	0.85 ± 0.11	−4.99 ± 11.50
Alcohol-based gel
Baseline	41.2 ± 9.0		0.92 ± 0.07
0 h	43.0 ± 9.5	4.1 ± 5.6	0.91 ± 0.08	−1.99 ± 5.10
2 h	40.1 ± 8.9	−3.1 ± 9.9*	0.92 ± 0.08	−0.76 ± 5.91
4 h	39.4 ± 8.8	−5.3 ± 11.8***	0.89 ± 0.09	−4.31 ± 7.37

Only the use of soap led to a progressive reduction of in skin moisture percentage after 2 h of treatment (baseline vs. 2 and 4 h, respectively; p < 0.001 and p < 0.05; Figure  and Table ). Similarly, alcohol based-gel treatment decreased corneometry values after 2 h of treatment when the percentage of moisture change was assessed (0 h vs. 2 and 4 h, p < 0.05 and p < 0.001, respectively; Table ).

Effect of hand sanitizer products on forearm skin elasticity

Skin elasticity was assessed by cutometry in both forearms. The technique evaluates skin deformation in different skin layers after a non-invasive repetitive sequence of tissue suction and relaxation, involving the different skin layers. No significant differences were observed at the beginning (baseline values). The percentage of elasticity change was compared, after the treatment, with the values obtained at 0 h, that is, immediately after the first cleansing procedure. Net elasticity and the percentage of elasticity change increased in the control skin (baseline or 0 h vs. 4 h p < 0.05, Figure  and Table ), in contrast to the effect observed in the soap treated skin, in which net elasticity diminished during the assay (baseline vs. 4 h p < 0.01, Table ). Skin elasticity did not change when cleansing was performed with alcohol-based treatments (Figure  and Table ).

DISCUSSION

According to the WHO, hand hygiene and face masks are the main way to prevent infection and spread of the SARS-CoV-2 virus. The first is a very simple procedure that reduces the microbial load of the skin. However, the products used for hand hygiene can gradually damage the different layers of the skin, affecting biophysical properties related to skin function such as moisture, transepidermal water loss (TEWL), pH¹⁰, and elasticity. This occurs mainly when cleansing procedures are repeated very frequently. Furthermore, people may experience adverse reactions such as dryness, irritation, and erythema. According to our survey, hand cleansing procedures increased during the COVID-19 pandemic as much as 2.5 times each day. Other studies found that the frequency of handwashing increased 1.7 to 5.7 each day. As has been reported, excessive hand cleansing (i.e., more than 10 times a day), increases the risk of skin damage. In the present study, 70% of respondents who had increased their hand hygiene habits, reported skin alterations such as dryness, irritation, itching, redness, and even skin wounds. Blistering lesions, bleeding fissures, and contact dermatitis have also been reported in other studies, but not by the respondents of our survey. In general, people reported a greater number of adverse reactions with alcohol-based gel than with soap, but the effects differ according to the product, ingredient concentration, contact time and frequency of use. Applying moisturizers after using alcohol-based products or handwashing can reduce the adverse reactions associated with excessive hand hygiene. Properties such as product consistency, drying time, sticky sensation, and fragrance influence the acceptability of the products and their side effects. Propanol and isopropanol have been shown to induce more skin redness and barrier function damage than ethanol. These findings correlate with in vitro studies where propanol and isopropanol cause increased expression of pro-inflammatory cytokines such as TNF-α and IL-1α by keratinocytes, as well as denaturing of proteins involved in barrier function. The results of these studies suggest that the excessive use of hand hygiene products could affect skin biomechanics as a consequence of changes in moisture and lipid barrier perturbation.

Skin damage due to excessive hand cleansing frequency has been linked to various damaging mechanisms related to unspecific removal of proteins and lipids, corneocyte removal and inflammation derived from corneal layer disturbance. Changes in TEWL, pH¹⁵, and microvascular blood flow have also been reported. It has been observed that repeated skin cleansing with liquid soap favors TEWL, triggers irritation, and skin barrier perturbation, even more than alcohol-based products. Different studies have focused on different body skin areas and time of use. Long exposure studies have focused on hands, while early skin damage studies have focused on undisturbed skin regions. We used volar forearm skin to evaluate moisture and elasticity of skin by cutometry—because hand skin may had been subjected to previous damage due to excessive hand hygiene during the COVID-19 pandemic, and previous research had already established the basic principles to measure different skin properties with this technique. Furthermore, the forearm has several advantages for skin assays; it is wide and easily available, has little hair and is considered frequently for dermatological product assessment, making it appropriate for comparing results between different studies.

The second part of the present study used information obtained by our research group and by others, with respect to excessive hand washing habits during the COVID-19 pandemic. Soap or alcohol treatments administered every 30 min during 4 h, mimicked the hand hygiene habits of health care personal during an active working day. Our baseline data for normal skin moisture agreed with the results of other studies. Soap was the hygiene product that was associated with the greatest changes in skin moisture, altering skin characteristics after 2 h of treatment. Otherwise, alcohol-based gel first increased and then maintained skin moisture levels. This effect may be associated with a moisturizing effect observed after the first administration of the alcohol-based gel. These results agree with previous studies that observed an increase in skin moisture after a single application of alcohol-based hand rub. The moisturizing effect of this formula is related to its glycerin content. The decrease in skin moisture observed in the present study after several applications of alcohol-based gel (2 and 4 h) did not fall below control values, indicating that short-term effects on skin did not impair skin moisture. It is possible that long-term treatments can alter skin characteristics, as reported in a three-day trial by Fallica F. (2021). This could be related to the damage done to the stratum corneum as a result of the product composition and the mechanical friction (rubbing) performed during application. The results of the present study agree with a previous study in which moisture diminished in skin treated with 0.5% sodium lauryl sulfate, a basic ingredient of several soaps, when compared with 80% ethanol.

Although different studies have failed to find a significant correlation between moisture levels and the elastic properties of the skin after the application of a moisturizer product, it is evident that a significant perturbation of the skin barrier, leading to water loss, do cause general skin stiffness derived from non-living epidermal layer disturbance. Since cutometry-based skin elasticity measures whole skin displacement and recovery by means of probe suction, it is evident that lower skin moisture derived from soap treatment can be related to net elasticity. A previous study using this suction method (cutometry) also found a decrease in skin elasticity after two daily washes for 7 days with an alkaline bar soap.

It has been observed that emollients or emulsifiers used in personal care products with high relative moistening performance induce low relative elasticity and vice versa. Thus, it seems that different molecular and/or biochemical mechanisms contribute to these two biophysical skin parameters.

In the present study, the progressive increase in skin elasticity observed in the control area was remarkable. The explanation of this phenomenon could be related to morning elasticity, which decreases due to skin alterations induced by hygiene habits such as morning showers. Changes in skin properties (pH, moisture, TEWL) after a single use of cleansing products have been reported as reversing to normal values after about 90 min. However, the effect of some products remained after 90 min or even after 12 h from the last washing. Soaps can remove dirt, but they facilitate the removal of the natural moisturizing factor also, by influencing physical properties of the stratum corneum (i.e., hydration and elasticity). It has been observed that by decreasing the natural moisturizing factor, intermolecular attractive forces of keratin fibers increase, while reducing molecular mobility, and favoring a decrease in the elasticity of the stratum corneum.

It is worth noting that the present study evaluated the short-term effects of hand cleansing in a small number of people. It would be necessary to carry out long-term studies with a larger people sample, including other quantitatively measurable biophysical parameters such as TEWL, pH, and erythema. It would also be important to study the time that skin requires for recovery. In conclusion, hand hygiene habits during the pandemic have changed, causing an increase in the frequency of the use of products to sanitize the skin. The excessive use of soap or alcohol-based products has caused dermatological problems in the population, highlighting the need to help the skin to recover using different moisturizers.

ETHICAL APPROVAL

Patients without skin lesions in the forearm completed an institutional consent form for their participation in this non-invasive assay (INRLGII 07/11).

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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