In this issue of “Hello Ingredient!” we tackle glycerine. Why? Because it might just be the most misunderstood cosmetic ingredient out there. Every now and again I see cosmetic products branded as “no glycerine” and I cannot comprehend why. In my research I read dozens of scientific reports on this key cosmetic ingredient and virtually none presented glycerine as a risk. Personally, I believe this old friend has fallen out of fashion and cosmetic companies simply had to demonise it to be able to create a trend for other (usually inferior) humectants.
What is glycerine?
Glycerine (also called glycerol) is a simple organic compound containing three hydroxyl groups (polyol). It is a colourless, odourless, viscous liquid. Glycerine is a humectant, which means, that it binds to the molecules of water. In fact, if you leave glycerine in an open dish in a humid environment, it will double in volume over three days.
How is glycerine made?
Glycerine is a by-product of soap production. It is very important to ensure the source of glycerine, as it can be derived from both animal and plant fats, as well as produced synthetically from propylene. Naturally Honest Labs use only organic vegetable glycerine in our products.
Is glycerine safe?
Yes. Glycerine is non-toxic and environmentally safe. Glycerine is naturally occurring in humans, animals and plant matter in combined form as glycerides in fats and oils, or, in intracellular spaces as the backbone of lipids. In fact, glycerine plays an incredibly important role. Glycerine deficiency can lead to increased moisture loss and poor elasticity of the skin.
A very short story of the skin
Let’s start with a very short explanation of skin’s anatomy and physiology. The outermost layer of the skin, called the epidermis, is locked in a never-ending cycle of death and rebirth. I’m afraid, as long as we live it will not achieve its nirvana. The death happens as the skin cells called keratinocytes are pushed upwards by the newly formed keratinocytes underneath them and as a result the ‘older’ keratinocytes are deprived of nutrients, which can only be delivered to the deeper layers of the skin. The dead keratinocytes (now called corneocytes) end up flattening and eventually create a form of a brick wall with lipids playing the role of mortar between the bricks. That brick wall is the skin’s barrier and makes our skin water and pathogen-resistant. On the other hand, it also helps to retain the moisture within the skin. As with every wall, also this one needs to retain its integrity to do the job properly. It is therefore very important to keep the outermost layer of our skin well hydrated, so that the skin can remain elastic, with a full protective capability and when the time comes – the cells should let go and shed with ease.
The role of hydrating these outermost layers of our skin falls with the Natural Moisturising Factor (NMF), which is a humectant produced by our own skin. With age, due to our genetics or because of the environmental factors our skin can become deficient in retaining an appropriate moisture balance and this is when conditions like atopic dermatitis, psoriasis, ichthyosis vulgaris and xerosis (dry skin) can occur.
Skin benefits of glycerine:
Glycerine binds moisture from the environment. By the same logic, glycerine applied to the skin will bind water from the environment in humid conditions. It then creates a persisting water reservoir within the skin. It does so without altering the skin’s normal physiology, because glycerine is already naturally occurring in human NMF.
Therefore, glycerine dissolved in a water based cosmetic or applied on a wet skin, will bind those water molecules within the top layer of the skin. If the environmental conditions change to dry, glycerine also acts as a great transmitter of the moisture from the deeper layers of the skin to the outer ones.
Moisturisation is a slightly different beast than hydration. It’s all about retaining the moisture rather than attracting it. It is the role of the lipids to fill the spaces between corneocytes and reduce the transepidermal water loss (TEWL). The ability of lipids to form an effective barrier can be influenced by genetic variations, ageing, dietary influences, seasonal effects and environmental factors.
Glycerine not only builds moisture reservoirs within the lipid structures but it also reduces the TEWL. Studies show, that Glycerol applied under controlled conditions (relative humidity not exceeding 65%, room temperature: 20◦C) limited the water flux from the skin’s surface. This in turn reduced the skin’s roughness.
Smoothness and Elasticity
The hydroscopic abilities of glycerine cause corneocytes to fill with water in a process called bulking. On the other hand, the occlusive properties (reduction of TEWL) of glycerine ensure that the moisture is trapped within the skin. This leads to smoothing of the skin’s surface and a long-lasting reduction in roughness. The hydration level of the outermost layers of the skin is also a great determinant of its elasticity.
Protection against environmental factors
Glycerine increases the resilience of our skin by bulking up the cells in the outermost layer of our skin (see above). It also prevents the lipids (the mortar between the corneocytes) from turning solid in dry conditions, therefore retaining their flexibility. Glycerine enables the skin lipids to preserve their normal structure even when underhydrated.
Stabilisation of collagen
Glycerine stabilises collagen’s triple-helical structure and protects it against denaturation. It becomes bound to collagen and replaces the previously attached water molecules, strengthening the structure.
Skin barrier repair
A number of studies have proven that topical application of a glycerine solution can protect the skin against the damage caused by abrasive substances like Sodium Lauryl Sulfate (SLS). The application of glycerine prior to washing the skin with SLS led to a faster reconstruction of the skin’s protective barrier. Glycerine, by absorbing water, can stimulate a water flux and aid the barrier repair. Up to seven days after the end of the treatment with glycerine there was an observable occlusive effect and reduction in TEWL.
Healthy cell turnover
It isn’t a secret, that not enough moisture in the skin or low humidity environment can lead to the skin becoming dry. What is interesting, though, is the reason for this. What appears as dry skin is really an amalgamation of dead skin cells at the very surface of the skin. The skin cells, which would have shed, under normal circumstances, are lingering on, leading to the thickening of the horny layer of the skin and its flaky appearance. It turns out that glycerine, by providing the necessary hydration, influences the activity of enzymes responsible for cutting off the bonds between corneocytes (a process known as desquamation) and therefore allowing for healthy cell turnover.
How to use glycerine appropriately
Glycerine should always be applied either previously dissolved in water or on a wet skin. Different literature quotes different optimal concentration levels, however, a 1/10 dilution is a good rule of thumb. After the application it is advisable to provide additional occlusion in the form of a face oil.
What do you think about glycerine now? Would you use it? Or perhaps you’re using it already. Let us know below!
Naturally Honest Labs’ products containing ORGANIC VEGETABLE glycerine:
1. Hydratone no1 Petitgrain
2. Hydratone no2 Palmarosa
3. “Smooth Operator” Body Butter
4. “Muscle Melt” Bath Oil
5. After Shave and Wax Oil
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