Last Updated on December 2, 2022 by Verna Meachum

If you have curls, you know that glycerin is often hailed as a curly hair nemesis, especially during summer.

But what is glycerin, and is it really good for your hair?

In this post, we’ll take a closer look at glycerin for hair and its effects.

We’ll also discuss how it works in your haircare routine. By the end of this post, you’ll be able to make an informed decision about whether or not to add glycerin to your haircare regimen.

Overview

Take a quick glance at the ingredients list of any hair care product, and you’re likely to see a recurring ingredient: glycerin.

In the curly hair community, folks have been debating the merits of glycerin for years.

Is glycerin good or bad for curly hair? The answer, it turns out, is a little bit of both.

Glycerin is a simple naturally occurring organic polyhydric alcohol. It is probably one the most common, frequently, and most abundantly used ingredients in personal care formulations, both skin and hair care products.

In simpler terms, glycerin is a humectant, which means that it has the ability to attract and retain moisture. This is why glycerin is often used in products that are designed to hydrate the hair.

The reason for its wide range of usage is because of its multifunctional benefits and the different roles it plays in a given formulation.

It is an excellent moisturizer, humectant, solubilizer, rheological modifier, and even sometimes stabilizer in a formulation.

Furthermore, it is an inexpensive (cheaper) ingredient and is easily available. Other than cosmetics, glycerine has a wide range of chemical applications in various industrial sectors.¹

In this short article, let’s explore this fantastic ingredient, some basic information, its role in curly hair care formulations and how can we get the best out of glycerin in our regimen.

So, What is Glycerin?

In scientific terms, glycerin is a simple organic molecule having three hydroxyl groups attached to the carbon chain. Its chemical structure is shown below.

It tastes slightly sweet and is a viscous liquid that easily dissolves in water. It is manufactured at a large industrial scale mainly as a by-product of the saponification process (soap making where vegetable fat or animal fat is hydrolyzed using sodium hydroxide).¹

Glycerine molecule is highly hygroscopic which means it attracts water molecules from the air. This inherent property defines the characteristic features of glycerin and its applications.

Other names for glycerine

Safety in Skin and Hair Care Products

Glycerin has been around for centuries. It can be added in concentration levels ranging from 2.0% to high up to 50% of the formulation (maybe even higher), depending upon the task and nature of the product.

There isn’t anything negative about its effect or safety hazard for skin and hair care consumers, which is great.

Recently, its safety and toxicology have been reviewed in the International Journal of Toxicology, and experts found glycerine safe in present-day cosmetics. So, no worries at all, it is perfectly safe to use.²

Also, it is a green and vegetable-derived naturally occurring ingredient, with no adverse impact at all.

Key Benefits to Hair

How Does Glycerin Work for Hair?

Glycerin is a humectant having good water binding ability and holding capacity. This feature is due to the presence of three hydroxy groups attached to the carbon chain.

Glycerin binds water molecules via hydrogen bonding. The magnitude of water molecules binding glycerin molecules depends upon osmotic pressure and humidity level (availability of water molecules in the air).

This characteristic property is exploited in hair care formulations.

Other examples of humectants are;

• propylene glycol
• sodium lactate
• sodium PCA, etc.^3-4

Glycerin-containing products (shampoo, conditioner, hair mask, or gel) attract water molecules which in the end raises the hair moisture level.

This moisture boost in hair fiber varies and depends upon multiple factors. The water holding capacity of hair varies with hair condition, protein level, porosity, damage, and external humidity level.

Porous hair fibers have a large pore size at the cuticle layer and thus more moisture levels can penetrate the hair structure.

Glycerin for hair: Good or bad?

Water is the key to hair life. Glycerin could be good for your hair, yet it may also have a negative impact.

Its efficacy depends upon hair conditions and external weather conditions. Glycerine significantly improves the hair moisture level and helps address the skin and hair dryness.

Hair dryness can indict significant hair damage. They become brittle, lose their shine and gloss, and also are difficult to style and manage.

Hair water uptake undergoes via a dynamic balance system where adsorption or desorption varies with varying humidity conditions.

It is a “Two Way Traffic” where hair absorbs or may desorb (lose) water depending upon the surrounding humidity. Moderate water absorption by hair is good for its health, quality, and outlook.

However, excess of everything is bad. Using high levels of glycerin may cause excessive water uptake, it swells and its diameter increases due to the high water level inside.

More moisture inside the hair fiber breaks the hydrogen bond of keratin protein and thus under high humidity conditions, hair becomes weaker and fragile.

Damaged hair fibers are more susceptible to this problem and are known to suffer severely. This is due to their higher porosity with more space for water molecules to fill in.

Glycerin for Hair During Summer and Winter

Glycerin works or behaves differently during summer and winter. The two seasons have different temperatures and humidity levels, and these two factors influence the hygroscopic activity of glycerin.

During summer, glycerin is an excellent choice for hair hydration therapy. The humidity is generally around 50-65 %RH level, thus having a balanced moisture level in the air.

A mixture of glycerin and natural oils or butter work to boost the hair’s moisture content, lubricity, and tactile properties.

However, conditions are the exact opposite in winter. The air is dry and the temperature is low. The humidity is also low and might also have frosty windy conditions.

Under these conditions, glycerin may not be a good option for your curls. Instead of drawing water molecules from the air, glycerin would attract water molecules from inside the hair and scalp cells.

That means, more water molecules outflow from the hair surface, making hair and scalp even drier.

Therefore, glycerine should be avoided in cold winter conditions (especially for curly and damaged hairs).

Instead, the better option is to use emollients and oils to preserve the internal moisture level, lubricate the surface, and minimize the water loss from the surface.

Summary

Glycerin is an excellent remedy for dry and damaged hair. It is inexpensive, easily available, and plant-sourced naturally occurring humectant.

Moreover, it is amazingly effective. It significantly improves hair moisture levels. However, care should be taken as it is not an ideal ingredient that can perform under all conditions.

Its performance is greatly affected by hair circumstances and external humidity conditions.

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References

1. Christoph, R.; Schmidt, B.; Steinberner, U.; Dilla, W.; Karinen, R., Glycerol. In Ullmann’s Encyclopedia of Industrial Chemistry, John Wiley & Sons: 2003.
2. Becker, L. C.; Bergfeld, W. F.; Belsito, D. V.; Hill, R. A.; Klaassen, C. D.; Liebler, D. C.; Marks Jr, J. G.; Shank, R. C.; Slaga, T. J.; Snyder, P. W., Safety assessment of glycerin as used in cosmetics. International journal of toxicology 2019, 38 (3_suppl), 6S-22S.
3. Loden, M.; Maibach, H. I., Dry Skin and Moisturizers: Chemistry and Function. Taylor & Francis: 2005.
4. Leyden, J. J.; Rawlings, A. V., Skin Moisturization. CRC Press: 2002.