Many people know that the active ingredient in the classic laxative glycerin suppositories is glycerin. Furthermore, many people use glycerin for skincare, or even apply suppositories directly to their face.
What exactly is glycerin? Is it really suitable for skincare? What are its effects and risks? Today, let's talk in detail about the familiar yet unfamiliar glycerin.
Glycerin is not actually an oil.
Glycerol is not actually an oil. Its scientific name is glycerol, with the molecular formula C3H8O3, and it is essentially a simple polyol compound. Physically, it is a colorless, odorless, non-toxic, sweet-tasting viscous liquid.
The history of glycerin dates back to 1779, when Swedish chemist Krzysztof Schell first attempted to produce it artificially. While boiling a mixture of olive oil and another lead-containing chemical, he separated a viscous, transparent liquid from the oily mixture, which he named glycerin because of its sweet taste.
During World War I, glycerol production surged as it became a raw material for gunpowder. Before World War II, glycerol production primarily came from the soap industry, with very little from natural plant and animal sources. After World War II, the rapid development of the petrochemical industry enabled the synthesis of glycerol via the propylene pathway, allowing for production through both the soap industry and chemical synthesis.
The use of glycerin has also become more widespread.
The applications of glycerin are not limited to the skin.
The development of the soap industry has made glycerin a major byproduct, and as a multifunctional compound, glycerin has a wide range of applications in many fields.
In the industrial field, glycerin can be used as an antifreeze and cryoprotectant, as well as in the production of paints, resins, gums and other coatings. It is even a basic component of various explosives and propellants (such as linear smokeless powder).
In the food industry, glycerin is used as a humectant, solvent, and sweetener, and helps preserve food. Additionally, glycerin aids in emulsification processes, and is therefore used in ice cream and many other processed foods.
In the pharmaceutical field, glycerin is not only used to treat constipation, but it is also an important ingredient in many cough syrups, ointments, expectorants, anesthetics, and lozenges.
In the personal care field, glycerin is widely used in toothpaste, mouthwash, shower gel, hair care products, soap, baby care products, and more. Its applications on the skin are particularly numerous, including but not limited to:
Moisturizing: Glycerin has strong hygroscopic properties and is a classic humectant, which belongs to the category of humectants.
Conditioning: Oils can improve the texture and appearance of the skin, making it smoother and more elastic.
Protection: Glycerin can form a protective film on the skin surface, which can prevent external environmental factors from irritating and damaging the skin to a certain extent.
Adjustment: Glycerin can adjust the viscosity of cosmetics, making them easier to apply and use.
Is glycerin used as a skin moisturizer?
Yes, but pay attention to the details.
Many people are interested in information about using glycerin for moisturizing. To sum it up, it can indeed be used for moisturizing, but there are some details to keep in mind when using it.
Glycerin can be used to moisturize the skin because, as a humectant, it can absorb moisture from the air, increase the moisture content of the stratum corneum, reduce moisture loss, and keep the skin soft and hydrated.
However, there are a few details to note before and during use:
1. Be alert for skin allergies
Glycerin is generally very safe and rarely causes side effects, but there is a risk of allergic reactions in rare cases.
Previous reports indicated that a 29-year-old woman developed contact dermatitis (a skin allergy at the point of contact) after using a moisturizer containing glycerin; her dermatitis improved after she stopped using the product. This suggests that glycerin can trigger allergic reactions in certain situations.
If you decide to use glycerin for moisturizing, pay attention to whether the area where it is applied develops redness, bumps, itching, or other skin abnormalities (while the areas where it is not applied do not show any skin abnormalities). If any of these occur, it is recommended to discontinue use and see a doctor promptly for treatment.
2. The concentration should not be too high, and pure glycerin should never be used.
The concentration of glycerin in skin care products should not be too high, and 100% pure glycerin should never be used. Previous data showed that applying 10% glycerin to a fixed skin area for 48 consecutive hours (patch test) can cause mild skin irritation and discomfort.
In addition, statistical data shows that the concentration range of glycerin in different skin care products is as follows:
Leave-on products (i.e., products that do not require rinsing after application, such as face creams, body lotions, and other moisturizing creams): glycerin concentration ranges from 0.0001% to 79.2%.
Rinse-off products (i.e., products that are rinsed off promptly, such as some types of face masks): Glycerin concentration range is 0.0007% to 99.4%.
Products for bathing: Glycerin concentration ranges from 0.66% to 47.9%.
The data above shows that glycerin is generally very safe and has a wide range of daily applications. It may be an almost negligible ingredient in skincare products, or it may be a key ingredient. However, generally speaking, it is not advisable to use too high a concentration. For example, for our most commonly used leave-on products, it is recommended to choose glycerin concentrations below 79.2%. However, there are no more specific concentration recommendations; you should observe the effects and side effects after using it yourself.
Ingredients of a common hand cream. Image source: Self-taken photo.
3. Whether it's easy to use or not ultimately depends on your own choice.
In skincare, from a dermatologist's perspective, glycerin is neither touted nor discouraged. This is because while glycerin does have effects, it's not the only effective moisturizer. What products to use for moisturizing skincare is ultimately an individual choice; there's no standard answer. Whether something is good or bad, and whether one is willing to use it, has a large subjective element. Some people prefer elegant packaging, some prefer portable designs, some dislike stickiness, and some prefer products with a pleasant fragrance…
On the other hand, some scholars have previously admitted that many types of moisturizers actually have quite good effects. It's important to understand that from the perspective of moisturizer development, initially there were only occlusive and hygroscopic ingredients (such as petrolatum as an occlusive agent and glycerin as a hygroscopic agent). Later, the skin's natural moisturizing factors appeared (such as lactic acid, pyrrolidone carboxylic acid, and amino acids), followed by formulas that repair the skin barrier in terms of structure and function (such as ceramides and polyunsaturated fatty acids). These ingredients can achieve moisturizing effects from different angles.
Therefore, the most important thing is to choose products that suit your own preferences; we don't need to favor one over another.
How do we determine what's right for us? Let's evaluate it from the following dimensions:
Personal experience: It does relieve dryness, roughness and other skin problems after use.
Safety: The ingredients are safe, and in particular, no abnormal reactions such as redness, granulation, or itching occurred at the application site due to the product.
Skin feel: It feels good on the skin, not particularly sticky, and I don't find it hard to resist using it.
Value for money: The price is not high, which meets my expectations; it's not a "luxury cream".
Brand: The brand is reliable; it specializes in skincare. Finally, let's briefly discuss whether it's appropriate to use glycerin suppositories on your face.
Our answer is—not really appropriate.
The ingredients of glycerin suppositories are very simple: glycerin and purified water. Theoretically, they do have a moisturizing and hydrating effect on the skin. The reason they are not suitable is not because they are ineffective, but because the concentration of glycerin is relatively high (52.8% to 62.5%), which may more easily cause skin irritation, and repeated use can easily lead to contamination.
If you want to use glycerin-based moisturizing skincare products, it's more appropriate to choose products specifically formulated for the skin.
Summarize
Glycerin, discovered nearly 250 years ago, is a remarkable compound with wide applications in many fields, including skin care. Its excellent hygroscopic properties provide moisturizing effects, but caution is advised regarding the risks of irritation and allergies. It's important to control the concentration and choose products that suit individual preferences.
Finally, it's important to emphasize that glycerin is just one of many moisturizing options; it's not a panacea, but it's certainly not useless. Hopefully, understanding the pros and cons of glycerin will allow everyone to choose skincare products that suit their individual needs more scientifically and rationally.
Author: Tang Jiaoqing, Attending Physician, Dermatology
Source: "Science Popularization China" WeChat Official Account
