Hand Sanitizer, Moisturizer and Emulsion

There is and will continue to be a higher demand for moisturizers and hand sanitizers

It doesn’t take too many “marketing people” to explain to a nerdy scientist like me how COVID-19 affects the beauty and personal care industry. This pandemic is shaping our hygiene habits, irreversibly. Consumers, like you and me, are demanding a greater amount of products, directly and indirectly, related to personal hygiene. Along with the obvious shortage of hand sanitizers comes the increasing demand for hand moisturizers.Sales for Avene’s hand cream in the United States have tripled in the past two to three weeks reported by The New York Times on March 11, 2020. Here let’s talk about hand sanitizers and moisturizers and how we may help you with the development of such.

Moisturizing is as important as sanitizing

On March 12, I was at San Jose airport flying back home. News came out the day before that three security officers had tested positive. So, I was sanitizing my hands as much as possible. Then I noticed two cracks on my hands, slightly bleeding. It struck me that I might get the virus into my system by simply touching a contaminated surface with my cracked hands –  without having to touch my face.

The shell of most virus, like the COVID-19, has fats and proteins as showed in Figure 1.

Soap disrupts fats; alcohol degrades proteins. They, therefore, kill the virus. But at the same time, they are causing damage to our skin barrier. The more we sanitize, the more we need to moisturize. In fact, WHO Guidelines on Hand Hygiene in Health Care has Provide HCWs (healthcare workers) with hand lotions or creams to minimize the occurrence of irritant contact dermatitis associated with hand antisepsis or handwashing (IA)[1]. Now with the majority of us having an increased amount of hand washing and sanitizing, we demand more skin moisturizers and will especially favor hand sanitizers that are more moisturizing and skin-friendly.

Figure 1. Sketch of COVID-19 structure, E, S, M are proteins. (Credit to Palli Thordarson, Professor, School of Chemistry UNSW) https://twitter.com/pallithordarson/status/1236549305189597189

Moisturizers and many hand sanitizers are emulsions

So, what moisturizes our skin?

Essential Ingredients in Moisturizers
CategoryIngredientFunctionCompound
Hydrophobic phase Occlusive agents and Emollients Fill the cracks in dry skin and make a film that prevents water loss, softens and smooths the skinpetrolatum, oil, wax, silicones, fatty acid
Hydrophilic phase HumectantsBond with water molecules and draw water to the skin from the dermis (the second layer of skin) to the epidermishyaluronic acid, glycerin, alpha hydroxyl acids, urea, honey 
WaterSolvent; Control rheological properties, e.g. viscosity, spreadability, etc.; Supplement skin water contentwater
EmulsifierSurfactantMixing the two phases into one, prevent phase separation, or, stabilize the mixturephospholipid, e.g. lecithin, etc.
Others e.g. rheology modifier, nutraceuticals, fragrance, buffere.g. better spreadability, anti-aging, present scents cellulose, vitamins, ceramide, fragrance
Blog 51878_Table 1.xlsx

Table 1 summarizes what we can find in a skin-moisturizing product and what they do to the skin.

The hydrophobic phase is the most essential component to keep skin hydrated. Vaseline, butter or soft cheese can get a dry skin back to normal. But most of us don’t favor the greasy feeling. Therefore, we also need a hydrophilic phase. To prevent a two-phase system as such from phase separation, we need emulsifiers, which are usually surfactants. The mixture of two immiscible liquids with one dispersed in the other is known as an emulsion. Figure 2 shows a typical emulsion droplet structure. Depending upon the volume fraction of the two phases and their viscosities, we gave them different names known as ointment, cream, lotion, etc.

Gels, in skincare language, refers to aqueous or alcoholic monophasic semisolid emulsion although some can be polymeric solutions as well. Many skincare gels are organopolysiloxanes-based emulsions, known as silicone emulsions [2][3]. They usually have a transparent appearance favored by consumers, especially when it comes to aloe vera gels. A study on aloe vera gel shows that its participants preferred a silicone-based formulation over an olive oil-based one for its textural properties, although the latter had a better hydration effect [4].

Hand sanitizers are usually gels that contain enough alcohol to kill germs. They are also emulsions in many cases [5][6]. In fact, Kimberly-Clark Worldwide, Inc. has its alcohol-based hand sanitizers as a high internal phase emulsion which allows moisturizers or skin protectants such as emollients and/or silicones to be stably incorporated into the sanitizer [5][6].

emulsion figure
Figure 2. Schematic Sketch of Emulsion Droplets Structures

In the next blog, I will talk about characterization tools for emulsion development, stay tuned!

Interested in Lunch & Learn with Malvern Panalytical to learn more about emulsion characterizations? Please contact your local Malvern Panalytical representative.

References:

  1. WHO Guidelines on Hand Hygiene in Health Care: a Summary First Global Patient Safety Challenge Clean Care is Safer Care,” 2009.
  2. US6423322B1 – Organopolysiloxane gels for use in cosmetics
  3. US4221688A – silicone emulsion which provides an elastomeric product and methods for preparation
  4. Moisturizing capacity of aloe vera gel in skin creams made with silicone-based and olive oil-based latex preparations.” Journal of Applied Cosmetology, 2004
  5. Moisturizing hand sanitizer”, Mar. 2008.
  6. US9775344B2 – High alcohol content sanitizer