Spectrum of Emerging Sciences, 2 (1) 2022, 56-65

The Influence of Soap and Alcohol-based Cleanser on Human Skin

Samrat Paudel^1,2, Rekina Shrestha^1,3, Pramod Poudel⁴, Rameshwar Adhikari^1,5*

¹ Research Centre for Applied Science and Technology (RECAST), Tribhuvan University, Kirtipur, Kathmandu, Nepal

² Kathmandu University, Department of Biotechnology, Dhulikhel, Kavre, Nepal

³ Himalayan White House International College, Department of Biotechnology, Purbanchal University, Khumaltar, Lalitpur, Nepal

⁴ Central Department of Biotechnology, Tribhuvan University, Kirtipur, Kathmandu, Nepal

⁵ Central Department of Chemistry, Tribhuvan University, Kirtipur, Kathmandu, Nepal

*Corresponding Author: Rameshwar Adhikari

E-mail Address: ram.adhikari.tu@gmail.com

Article available online at: https://esciencesspectrum.com/AbstractView.aspx?PID=2022-2-1-12

Introduction

Hand hygiene which includes handwashing with soap and water and/or cleaning hands with alcohol-based sanitizer is one of the simplest yet effective measures to control infections [1]. Proper and frequent handwashing can prevent gastrointestinal and respiratory diseases such as cholera, diarrhea, dysentery, typhoid, and soil-transmitted helminth infections [2–4]. The concept of handwashing to prevent infection has been in existence since very old age. In 1824 AD, Germain Labarraque, chemist and pharmacist found the occurrence of puerperal infection, fever, and maternal death rates can be decreased with handwashing [5,6]. Even though people knew about the importance of hand hygiene, it is still not taken seriously as it should be. Many people around the world don't have access to hand washing. Data shows the global population lacking access to hand washing during 1990 was 33.6%. The percentage of the population lacking access to handwashing in 2019 is still 26.1%. The comparison between the percentage of people lacking handwashing facilities in 1990 and 2019 has been presented in Fig. 1 [7].

After the COVID pandemic originated in December of 2019, the perspective of people towards health and hygiene, specifically hand hygiene has changed. In addition to the general public, there is increased compliance to hand hygiene practices during the pandemic among the health workers. This change in perspective has greatly reduced cases of hospital-associated infections [8–10].

While on one hand, more people are washing hands than ever, there are also numerous cases of skin deterioration due to the frequent use of soap and alcohol-based sanitizer. Dermatological conditions like eczema are prevalent among many people [11,12]. Research conducted in Thailand among health workers and non-health workers showed the presence of hand eczema in 20.87% of the study group [13]. Such a condition is more common in health workers as handwashing is more frequent in them compared to other people [14–17].

It is necessary to be aware of such side effects while using soap and alcohol-based cleansers for hand washing and cleansing. There is an immediate need to use soap and cleanser in a way that doesn’t hamper the normal physiological condition and surface integrity of the skin. With this article, we aim to disseminate better ways to use soap and alcohol-based cleansers so that hand hygiene can be maintained without compromising skin homeostasis.

Soap and cleanser are substances designed to remove dirt, sweat, sebum, and oil from the skin. Detergent-based soaps; synthetic detergent-based soap (Syndets), alcohol and alcohol-based gel are some of the common cleansers in practice. Soaps are the long-chain fatty acid alkali soap with a pH between 9

and 10 [18,19]. Most of the cleansers except alcohol-based disinfectants contain surfactants on them. The surfactants present in the cleanser not only aids in the upliftment of dirt and solubilization of oils but also remove the unwanted materials from the skin surface and promote normal exfoliation thereby rejuvenating the skin. Cleansing materials are important to maintain proper health hygiene well as they protect from microbes, mainly bacteria, and viruses [20,21].

However, on the negative side, the surfactants present in the cleanser can cause damage to the protein and lipids of the skin surface which leads to dryness, tightness, irritation, itching as well as barrier damage. For instance, sodium laurate, a twelve-carbon fatty acid, is a constituent of most soap which is considered to cause more skin irritation than other constituents [22,23]. The frequent use of soap and detergent-containing cleanser create problems to the skin like disturbance of natural pH, disturbing the natural microflora of the skin, and destroying the lipid and protein layer of the skin [24].

A better and skin friendlier cleanser should minimize the damages caused to the skin and should be able to deposit beneficial lipids on the skin. They also should be able to maintain the skin's hydration and moisture [25]. A good cleansing agent must combine disinfection and antimicrobial activity with the maintenance of skin homeostasis. A good cleansing agent must combine disinfection and antimicrobial activity with the maintenance of skin homeostasis. But the use of cleansing material comes at the cost of an increase in skin pH, decrease in moisture of the skin, disturbance of skin microflora, and lipid integrity.

2. Application of soap and alcohol as a disinfectant

The unique structure of a soap molecule contains both hydrophilic and hydrophobic ends responsible for the cleansing action of the soap. One end of a soap molecule is hydrophobic whereas the other is hydrophilic.

The general cleansing action of a typical surfactant molecule is achieved by binding the hydrophobic end with oily substances and hydrophilic end with water molecule is illustrated in Fig. 2. [26]. Now, the oily particles from the skin surface attached with hydrophobic ends are suspended in water and eventually washed away [20].

In addition to the cleaning action, the presence of hydrophobic and hydrophilic ends in surfactant molecules makes it possible to kill the viruses. The surfactant does so by the destruction of the lipid layer of the enveloped viruses like Coronavirus. The general mechanism of this process is illustrated in Fig. 3. The hydrophobic end of the soap molecule binds with the outer lipid membrane of the virus. A 20-second wash will break the membrane leaving only the RNA of the virus and making it ineffective to cause disease. The germs are also removed by simple mechanical action during washing [27].

Alcohols such as ethyl alcohol, isopropyl alcohol, and propanol are commonly used as antimicrobial agents although several other alcohols can be effectively used [28]. Alcohols are widely used for surface disinfection, hard-surface as well as skin. Other antimicrobial agents such as chlorhexidine can be added in small quantities to the alcohol to boost its antimicrobial activity. Other excipients are also used with alcohol to decrease the evaporation time of the alcohol [29]. Even though there is not much known about the working mechanism of the alcohol, it is believed that alcohol in the combination of water (generally 70% of ethanol in water (v/v)) causes damage to the membrane and denature the protein which ultimately causes interferes with metabolism and cell lysis [28,30].

3. Risks and hazards of soap and alcohol-based cleanser

3.1   Disturbance to the natural pH and resident microflora of the skin

The natural pH of human skin is acidic and it acts as a barrier for pathogenic bacteria. This barrier is commonly known as the “acid mantle” [31]. The acidic pH, as well as concomitant pH over the stratum corneum (SC), are beneficial for a good skin condition, maintaining natural microflora in the skin as well as for forming an optimal structure of the lipid barrier and SC homeostasis [32–34]. The acidic pH on the skin surface helps in the growth of resident microflora, the microbes commonly found in the skin, and checks the growth of transient microflora which are opportunistic and potentially pathogenic [35]. The example of resident microflora includes members of Staphylococci, Micrococci, Coryneforms, and Cropionibacteria while transient microflora includes Gram-negative bacteria like Escherichia and Pseudomonas spp., Gram-positive, coagulase-positive Staphylococcus aureus, and Candida albicans [36]. The most common resident coccus is S. epidermidis which represents more than 80% of the total microflora of the dry body areas like arms, legs, and lower torso [37].

Resident microbes have a mutualistic symbiotic relationship with the skin. The microbes get the right biotope as well as lipid (sebum), minerals (sweat), and protein (dead skin cell) from the skin [38,39]. Microbes in turn strengthen the first line of defense in the skin. The resident microflora produces beneficial free fatty acid and prevents the colonization of the skin by harmful microbes from the surrounding area. The normal acidic pH of the skin is also maintained by the microbes living on it [36,40]. It is also seen that the antimicrobial effects of antibacterial protein and lipids of the skin are boosted at an acidic pH which is explained by the fact that uncharged lipid and cationic peptides interact better with microbial membranes [38,41,42].

The soap and soap-based cleansers are alkaline and they change the natural acidic pH of the skin to alkaline or higher pH range [43]. The study indicates the alteration of skin pH is an important factor that induces skin irritation. Skin irritation caused in adults needs a long recovery time and frequent exposure to soap affects the appropriate skin repair [44]. However, researchers argue that the pH changed by the use of soap is restored to a normal level after a while [37,44]. The restoration time might differ from 2 hours (after 5 minutes wash) [45] and some even took several hours (after 2 minutes wash) [46]. But there is no argument that the use of soap causes a significant change in the pH of the skin surface.

3.2   Dehydration of skin surface

For the proper maturation of SC, skin desquamation, and shedding of the outermost layer of membrane or layer of tissue, the water content of the SC must be optimal. The increase in transepidermal water loss hampers the functioning of enzymes responsible for normal desquamation which results in the visible appearance of dry and flaky skin [47].

The surfactant present in the soap binds to the SC proteins which cause transient swelling and hyperhydration during the wash. This is followed by evaporation of the water due to the de-swelling of the proteins [48]. It has been also studied that during swelling the surfactants and other cleansing agents penetrate deeper layers and induce biochemical responses like irritation and itch. The damage processes in the skin have been illustrated in Fig. 4 [49]. The binding of surfactants compromises the ability of skin protein to bind with water and retain it. This in turn causes the lower hydration of skin after washing [48, 50].

The reduction in water content of the skin causes a change in the skin’s viscoelasticity which is seen as after-wash-tightness of the skin within minutes after wash [51]. Moisturization of the skin is important to maintain an optimal level of hydration and plasticization since they retain the normal viscoelasticity of the skin [52]. Moisturization processes ensure the proper extensibility and flexibility required for skin movement. Various problems like lack of flexibility, visible dryness, skin roughness, scaling, and cracking are observed in the absence of adequate moisturization. To an extreme degree lack of moisturization can even lead to irritation in the form of erythema and itching [25]. The nature of the surfactant as well as the cleansing condition determines the extent of the damage.

3.3   Damage of lipid and protein present on the skin surface

There are different lipids and proteins found on the surface of healthy individuals. Lipids like free sphingoid bases and fatty acids [41] and epidermal proteins like cathelicidins, defensins, and dermcidin in the sweat play an important role in the cutaneous innate immunity [42, 53]. In addition, peptides present on the skin surface protect against the invasion of pathogens. Known as antimicrobial peptides, they form a chemical shield around the surface of the skin and are believed to trigger and coordinate various components of innate and adaptive immunity [53, 54].

There is scientific evidence of the damages caused by the use of surfactant compositions on human skin. The detergents and other cleansing agents in the soap have been found to cause damage to the lipid and protein in the human skin. It was found by the study using Transmission Electron Microscopy (TEM) that both lipid and protein regions are significantly damaged after washing with soap. Fig. 5 [55] is a TEM image exemplifying the damage caused by the surfactant to the skin [25,55].

Surfactants above their critical micelle concentration (CMC) are capable of solubilizing lipids of SC and causing delipidation [50]. Further, the adsorption and intercalation of surfactants into the SC lipid bilayer also damage the lipid. It results in increased permeability of the skin membrane and even lipid bi-layer destabilization [56, 57]. The level of fatty acid and cholesterol in the skin is significantly reduced even after a single wash if anionic-amphoteric surfactant is used without any moisturizing agent. Not only might this but the entire lipid biosynthesis process be altered due to the use of surfactants which will change the level of various lipids [58].

In a study to see the effect on the confirmation of protein by surfactants, the conformation of Bovine Serum Albumin (BSA) was changed significantly by surfactant. The same study has correlated the relationship between skin roughness and change in conformation of BSA [59]. The damage of skin proteins occurs by the interaction with keratins and their denaturation. The swelling of the cell membrane and collagen fibre as well as cytotoxicity expressed with cellular lysis also causes protein damage [60]. The denaturation of alpha-helical keratin caused by unfolding the coiled polypeptide chain due to surfactant – SC interaction was suggested in in-vivo experiments too [48]. This reversible change in conformation of keratin has been linked with surfactant-induced swelling of various membranes [61].

4.      Safety and sustainable uses

4.1   Approaches to Minimize the Damage

Even the damage due to soap and detergents is prominent, one cannot deny the role they play in maintaining hygienic and warding off pathogens. Regular use of soap containing triclocarban was found to reduce the incidence of impetigo among children by 47% in a study done in Karachi, Pakistan [62]. Another case-controlled study suggests the decreased risk of illness from Cholera in the individual who washed hands with soap before a meal [63].

To mitigate the damage to the skin caused by soap, they have been replaced with synthetic detergent-based bars or liquids known as syndets which are composed of non-soap synthetic surfactants like fatty acid isethionates and sulfosuccinic acid esters [64]. Syndets are mostly neutral or acidic and don't change the pH of the skin after use [43]. The syndets were found to show significantly less irritancy than soap bars in soap chamber tests [65].

Another attempt to reduce the side effects of soap is to incorporate glycerol in the soap. However, glycerol cannot be delivered effectively during the wash and the benefit of glycerol cannot be exploited in making soap. Even better than the glycerin-based lotion, oil-based lotions containing mineral oil, petrolatum or lanolin, are skin friendlier [66]. A formulation containing polysaccharides from okra (Abelmoschus esculentus) was able to provide adequate hand hygiene without causing irritation and significant skin drying. The formulation also maintained skin hydration for the observation period of 210 minutes [33]. It has been studied those liquid cleansers can be designed in a way to deposit beneficial lipids such as cholesterol and fatty acids during the wash [67]. It was shown with an in vivo study where a moisturizing body wash containing 20% triglyceride oils and 0.5% sterol was able to deposit about 10 μg/cm2 of triglycerides and 0.6 μg/cm2 of cholesterol on the skin surface during the wash [68]. While using surfactant-containing products it is wiser to choose one with a nonionic surfactant as it has a less skin-irritating tendency. Therefore, a cleanser with nonionic surfactants and silicone surfactants is a better cleanser. Silicone surfactants like dimethicone can penetrate follicles and remove debris as well as provide an emollient to soften the skin and check transepidermal water loss [69].

Additionally, the use of lukewarm water instead of cold water and properly drying the hand after washing also helps to mitigate the undesirable effect of soaps. During long work hours, gloves can be used which limits the need to wash the hand frequently [70]. All these techniques can be followed to prevent skin drying and irritation from the frequent use of soap while preventing the infection from COVID and other communicable infections. 

4.2   Alcohol-Based Gel: An Alternative to Detergent Based Cleansers

The alcohol-based gel has been commonly used as a cleansing material and also as a hand disinfectant. Different studies suggest alcohol and alcohol-based gel be superior to detergent-based soaps. Even when used repeatedly the effect on skin by alcohol was lesser than the effect on skin by detergents [71]. The alcohol-based disinfectant was found to be better at reducing the number of bacteria on hand than washing. Even without standardization, disinfection using alcohol was robust [72]. They are also regarded as more skin-friendly than detergent-containing products [73]. The alcohol-based gel was able to decrease the pH of the skin to a value where the pH could be favorable for the initiation of the epidermal barrier recovery and normal SC integrity. In a study of skin conditions in association with the use of alcoholic gel, a gel containing high levels of glycerin and ethanol (70% v/v) was found to be the most preferred formulation [74].

The prime advantage of using alcohol and alcohol-based disinfectant is that it is quite effective to control the Coronavirus. Alcohol can be used in disinfecting lipid enveloped viruses which include Herpes viruses, paramyxoviruses (measles, mumps), retroviruses (HIV, AIDS), Hepatitis B virus, and Corona Viruses. But it should be considered that naked virus families i.e., viruses without envelopes like adeno, parvo, and picorna are resistant to alcohol and common disinfectants [75].

The alcohol-based gel, however, isn’t without limitation. There are some practical limitations in the use of alcohol and alcohol-based gel as cleansing material and hand disinfectants.  First of all, alcohol is used more effectively as a disinfectant rather than a cleansing agent. The antibacterial activity of alcohol is reduced with the presence of dirt. Same as that of detergents, alcohol-based gel causes dryness and burning sensation in the skin to some extent due to the presence of short-chain alcohols [76]. But the overall irritation and soreness on the skin was found to be lesser in comparison with handwashing [72] and can be a substitute to the detergent-based soap whenever available.