Recently, hand care has experienced an unprecedented boom in consumer demand due to a heightened focus on sanitization and moisturization in response to the COVID-19 pandemic. Due to the pressurized market, regulations surrounding the manufacture and distribution of sanitizing products have been temporarily relaxed by governments1, 2 across the world. Disruptions in supply have led to several non-cosmetic companies, and indeed consumers themselves,3 trying their hand at sanitizer manufacturing.
Unfortunately, this amplifies risks to the consumer due to the heightened potential for dosage miscalculations or unwanted impurities (such as benzene and gasoline)4 from non-cosmetic grades of ethanol. Due to the pressure on ethanol manufacturing, methanol contamination has also become alarmingly widespread and resulted in the U.S. Food and Drug Administration (FDA) sending warnings to consumers and companies over thousands of hand sanitizers, and recalls during the height of the pandemic.5, 6
To cope with the crisis, the personal care industry has concentrated on getting more products to market quickly. However, through this, the formulation challenges and manufacturing complexities of cosmetic development have been felt across the world. As we move into the “new normal,” the focus of formulation work must be shifted back in line with market regulations to create high quality, safe products in the longer term.
In relation, the present article explores key aspects of formulating safe and effective hand care products for today’s consumer needs. It considers core aspects of skin barrier functioning and various means to address disruptions therein. It also offers solutions to reduce irritation, restore balance and provide protection to prevent further damage.
Importance of Hand Care
As manufacturing processes changed in response to the crisis, so too have consumer behaviors—40% of consumers now wash their hands between 6 and 10 times a day.7 Regular use of alcohol-based gels or surfactants is usually well-tolerated, however, repeated exposure can lead to chronic cumulative irritant contact dermatitis due to the removal of skin surface lipids, denaturing of epidermal keratin, damage to skin proteins and, in rarer cases, alterations in the cell membrane of keratinocytes. Additionally, wearing protective gloves stimulates excessive sweating and increases humidity, inflating the inflammatory response toward irritants such as these.8, 9
The skin barrier acts as the immune system’s first line of defense.10 Fatty acids in sebum form an “acid mantle” that inhibits the growth of pathogenic species.11 The lipid bilayer directly inhibits some microbes, such as S. aureus, and supports other beneficial microbiota.12 Structural cells such as keratinocytes, fibroblasts and adipocytes form a mechanical barrier against pathogens and play a key role in expressing inflammatory cytokines. Immune cells in the epidermis and dermis, such as Langerhans cells and dermal macrophages, directly tackle infection. And, the skin’s surface plays host to an extensive microbiome that modulates growth of pathogenic bacteria, fungi, viruses, molds and yeasts.
It has long been known that disruptions to this complex barrier can increase the risk of infections for example, in burn patients or those with a thinning or broken skin barrier, such as the elderly or those with eczema. Through studies of health workers, it has been shown that intensive hand-washing can lead to an increased incidence of occupational skin diseases,13 mainly because only 22% of health workers are applying restorative skin cream after washing to help protect the skin barrier.14 The medical importance of regular hand-washing cannot be understated, so to alleviate disruption to the skin, formulations need to focus on repairing, protecting and enhancing the skin barrier whilst allowing for effective cleanliness.
Addressing a Disrupted Skin Barrier
One of the key goals to consider when formulating hand care is to mitigate the effects of dryness, which occurs when skin lipids are continuously removed from the skin surface. This is often approached in three ways: reducing trans-epidermal water loss (TEWL) through boosting or supplementing the Natural Moisturizing Factor (NMF); replenishing intercellular lipids; and optimizing the cellular arrangement in the stratum corneum to allow efficient diffusion of water through the skin.
Reducing TEWL: The NMF contains a mixture of water-soluble humectants that draw atmospheric water into the skin, the most famous of which is hyaluronic acid. This acts as a powerful hydrating agent and can provide rapid and intense hydration, with careful formulation allowing for both immediate and long-term hydration through layering of the molecular weights or using optimized cross-polymers. The skin’s natural production of hyaluronic acid can also be boosted using active ingredients. Examples may include specialized extracts of prickly pear15 or Australian plums,16 and sugar derivatives such as xylitylglucoside, anhydroxylitol and xylitol,17 which influence gene expression related to hyaluronic acid production.
Whilst hyaluronic acid is the most widely recognized component of the NMF, the bulk (~40%) is composed of amino acids.18 These can be added to hand care formulations through blends that optimize the ratio of different amino acids, amino acid derivatives such as betaine, or through natural extracts such as certain algae19 that contain naturally high levels of amino acids. Similarly, the introduction of humectants such as glycerin, urea or panthenol (provitamin B5) can be used to supplement the NMF by reducing TEWL, although these can introduce formulation difficulties, as will be discussed later.
Replenishing intercellular lipids: Emollients such as shea butter and olive oil are regularly included in hand creams to form an occlusive barrier that helps to both prevent water loss and replenish the lipids lost through hand-washing. To optimize lipid replacement, sebum mimetics such as jojoba oil or squalane can be added, as well as specifically designed blends20 rich in linoleic, oleic and palmitic acid to replicate the composition of lipids in healthy skin. This concept can also be used within hand washes. For example, a specialized blend of lipophilic plant components has been shown to improve the hydration of skin by 100% when used at 0.50% in a hand wash, as it has been developed to mimic both the composition and structure of the skin, with long-lasting effects on skin hydration and smoothness.21
While free fatty acids comprise roughly 30% of the intercellular lipids, traditionally overlooked by hand care are the 40% from ceramides.22 As hand care increasingly draws inspiration from luxury facial care, the number of hand products containing ceramides is growing. The skin’s natural level of ceramide III, also known as ceramide NP, has been shown to be particularly diminished by surfactant-induced dermatitis.23 It is possible to apply ceramide III topically through well-formulated hand care products; however, this can introduce formulation difficulties as ceramide III is only soluble in oils at elevated temperatures (90°C/194°F). There are variants designed to overcome this, for example, by introducing a double bond to reduce processing temperatures to 75°C/167°F, or by forming pellets with cetearyl alcohol for easier processing.
Optimizing cellular arrangement in the stratum corneum: In hand creams, lotions and masks, the choice of emulsifier can also supplement the skin barrier, with liquid crystal technology enabling greater compatibility with the skin’s lamellar bilayer lipids due to their similar chemical structure. Similarly, a texturizing agent based on C10-18 triglycerides enhances affinity with the skin’s (triglyceride-containing) hydrolipidic film, whilst giving the formulation greater creaminess and longer playtime.24
While the emulsifier can help to mimic the skin’s lamellar structure, the skin structure itself can also be improved through active ingredients. For example, an exopolysaccharide from the deep sea extremophile Alteromonas, as a fermented extract, has been shown to protect Langerhans cells, reduce the expression of skin stress marker ICAM-1 and stimulate keratinocyte proliferation, leading to an improved skin barrier and activation of the skin’s restructuring processes.25
Soothing hand masks: Although dryness is the primary concern for consumers, when the skin barrier is compromised, this leads to itching and irritation, which will aggravate the damage even further if consumers scratch or abrade the skin. Currently, the British Association of Dermatologists and National Eczema Society both recommend using soap and water for hand-washing—even for those with eczema or other skin concerns, overriding the pre-COVID-19 advice to use mild soap substitutes.26, 27 To relieve the irritation this causes to sensitive skin, intensely soothing formulations such as overnight hand masks are soaring in popularity.
Conventionally, creams targeting soothing claims utilize allantoin, lanolin or urea; however, these can create heavy, tacky textures, especially in combination with glycerin. Responding to concerns over lanolin irritation from pesticide residue in sheep’s wool,28 the industry has shifted toward purer grades and vegan alternatives, and toward optimizing emulsifier combinations to reduce greasy textures. One solution is to use a combination of lecithin, hydrogenated lecithin and sodium acrylates copolymer to create a non-tacky texture even when using 20% glycerin and 5% urea.29
Newer soothing ingredients are available, and those with data supporting fast results are particularly suitable for the instantaneous effect necessary for hand masks. One specific extract of Helichrysum italicum has been shown to stimulate the release of b-endorphins and decrease inflammation mediators, with in vivo testing showing a decrease in stinging sensation within 1 min, and a decrease of 79% versus the control in 5 min.30 Similarly, an extract of Tasmanian pepperberry has been shown to dim the inflammatory cascade within 5 min; it contains high levels of rutin, an anti-inflammatory mediator known to strengthen capillaries.31
Another recent introduction with powerful soothing activity is based on a patented concentrate of peptides from the microalgae Chlamydomonas acidophila. This ingredient inhibits the inflammatory response of TNF-a, prostaglandin E2 and PGE2 release in response to mechanical stress, such as from surfactants, and has been shown to help boost hydration and strengthen the skin barrier. Interestingly, this has also been shown to help regulate the skin’s reaction to nickel (a prominent allergen-mimicker), with potential use in hand care to alleviate the cosmetic effects of sensitization reactions from wearing nickel-containing jewelry.32
As a more traditional alternative, another ingredient currently trending in skin care is Centella asiatica, also known as cica, gotu kola or tiger’s grass. Rich in triterpenes such as madecassoside and asiaticoside, extracts from this plant have been shown to help soothe reactive skin, and improve skin roughness and moisturization.33 Used for centuries in Indian ayurvedic medicine and traditional Chinese medicine, consumer-led trends indicate rising interest in these practices and the use of Centella asiatica in hand care is showing promising potential.
- Duckett, A. (accessed 2020, Aug 25). UK relaxes rules to speed up sanitizer production. Available at: https://www.thechemicalengineer.com/news/uk-relaxes-rules-to-speed-up-sanitiser-production/
- Mishra, M. (2020, Mar 20). U.S. FDA to relax hand sanitizer regulation as coronavirus hits supply. Available at: https://www.reuters.com/article/us-health-coronavirus-hand-sanitizers/fda-to-relax-hand-sanitizer-rules-amid-coronavirus-outbreak-idUSKBN217287
- Pratt, E. (2020, Jul 6). Why you might want to think twice before making your own hand sanitizer. Available at: https://www.healthline.com/health-news/coronavirus-hand-sanitizer-recipes-risks
- Hahn, S.M. (2020, Jun 1). Coronavirus (COVID-19) Update: FDA takes action to protect public health; Increase supply of alcohol-based hand sanitizer. Available at: https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-takes-action-protect-public-health-increase-supply-alcohol-based
- Kahn, J. (2020, Jul 2). Coronavirus (COVID-19) update: FDA takes action to warn, protect consumers from dangerous alcohol-based hand sanitizers containing methanol. Available at: https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-takes-action-warn-protect-consumers-dangerous-alcohol-based-hand
- Kahn, J. (2020, Jul 27). Coronavirus (COVID-19) update: FDA reiterates warning about dangerous alcohol-based hand sanitizers containing methanol, takes additional action to address concerning products. Available at: https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-reiterates-warning-about-dangerous-alcohol-based-hand-sanitizers
- Tandon Copp, L. (2020, Apr 29). 40% of Consumers now wash their hands 6-10 times a day to avoid COVID-19.Available at: https://cosmeticsbusiness.com/news/article_page/40_of_consumers_now_wash_their_hands_6-10_times_a_day_to_avoid_Covid-19/164583#
- Beiu, C., et al. (2020). Frequent hand-washing for COVID-19 prevention can cause hand dermatitis: Management tips. Cureus 12(4) 7506; doi: 10.7759/cureus.7506
- Khosrowpour, Z., et al. (2019). Effects of four soaps on skin trans-epidermal water loss and erythema index. J Cosmet Dermat 18(3) 857; doi: 10.1111/jocd.12758
- Chambers, E.S., et al. (2019). Skin barrier immunity and aging. Immunology 160(20) 116; doi: 10.1111/imm.13152
- Fluhr, J.W. et al. (2001). Generation of free fatty acids from phospholipids regulates stratum corneum acidification and integrity. J Invest Dermatol 117(1) 44; https://doi.org/10.1046/j.0022-202x.2001.01399.x
- Moran, J.C. et al. (2017). Comparative transcriptomics reveals discrete survival responses of S. aureus and S. epidermidis to sapienic acid. Front Microbiol 8(33); doi: 10.3389/fmicb.2017.00033
- Elston, D.M. (2020). Occupational skin disease among health care workers during the coronavirus (COVID-19) epidemic. J Am Acad Dermatol 82(5) 1085; doi: 10.1016/j.jaad.2020.03.012
- Yan, Y., et al. (2020). Consensus of Chinese experts on protection of skin and mucous membrane barrier for health-care workers fighting against coronavirus disease 2019. Dermatologic Therapy e13310; doi: 10.1111/dth.13310
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- British Association of Dermatologists (2020, Mar 3). COVID-19 (coronavirus): Statement on dry skin and frequent handwashing to reduce COVID-19 risk. Available at: https://www.skinhealthinfo.org.uk/statement-on-coronavirus-and-skin-disease-affecting-the-hands/
- National Eczema Society (2020, Mar 23). Advice on coronavirus (COVID-19) for people with eczema. Available at: https://eczema.org/blog/advice-on-coronavirus-covid-19-for-people-with-eczema/
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