Glycerin is often hailed as a nemesis for curly girls, especially during summer. But whether this is accurate or not is up for debate. When considering products that include glycerin, you may ask what glycerin is and whether it is good for your hair.
Glycerin for hair has pros and cons. It is good because it helps your hair retain moisture while adding softness and smoothness. This is especially helpful for curly hair that requires extra hydration. But too much glycerin can also make the hair greasy and lead to buildup.
I’ve partnered with my friend, a hair scientist and Cosmetic Formulator to provide a trustworthy perspective on glycerin and hair. Together, we delve deep into the effects and mechanisms of glycerin on hair, ensuring you have the information you need to consider its inclusion in your hair care routine.
Glycerin in Hair Products
Glycerin, a colorless liquid, is a common ingredient in hair care products. This simple, naturally occurring organic polyhydric alcohol is widely used in personal care formulations for skin and hair products.
The debate over whether glycerin is beneficial or detrimental to curly hair types has persisted in the curly hair community for years, and the answer lies somewhere in between.
Renowned for its humectant properties, glycerin attracts and retains moisture, establishing it as a favored ingredient in hair and beauty products. Its versatility is attributed to its multifunctional benefits, serving as an excellent moisturizer, humectant, solubilizer, rheological modifier, and occasional stabilizer in various formulations.
Beyond cosmetics, glycerin finds application in different industrial sectors due to its affordability and widespread availability.1 It is known by alternative names such as:
- Glycerine (British English)
Glycerin is known by other names, such as:
- Glycerine (British English)
Glycerin vs Castor Oil
While glycerin and castor oil are frequently compared, they have both similarities and distinctions. Commonly utilized in skincare and haircare products, these two ingredients often work together to complement each other’s properties.
Glycerin functions as a humectant, drawing in and preserving moisture, thereby promoting hydration and preventing dryness. It plays a key role in maintaining the water balance in both hair and skin.
Castor oil is recognized as a natural humectant, valued for retaining or restoring moisture by preventing water loss through the outer layer of the skin. Enriched with fatty acids, castor oil offers profound hydration, promoting overall hair and scalp health.
Safety of Glycerin in Skin and Hair Care Products
Glycerin, a centuries-old popular ingredient, has a long-standing reputation for safety, with no known adverse effects for skin and hair care consumers.
For those with curly hair, the safety of glycerin has never been a major concern. This versatile ingredient can be added in concentrations ranging from 2.0% to potentially 50% or more, depending on the product’s task and nature.
Derived from vegetables, glycerin is a green and naturally occurring element that poses no adverse impact. Recent reviews in the International Journal of Toxicology confirm its safety in modern cosmetics, assuring users that glycerin is perfectly safe for use in hair care formulations.2
Key Benefits of Glycerin on Hair
When examining ingredients in hair care products, individuals typically focus on their benefits, aiming to choose components that contribute to the overall effectiveness or serve as essential elements in the formulation, ultimately promoting healthy hair.
Glycerin has several benefits for your hair, such as:
- It is an excellent moisturizer for the hair shaft.
- It improves your hair’s moisture level.
- It addresses the issue of dryness.
- It combats flaking and redness.
- It has an ideal safety profile with low toxicity.
- It enhances the formulation’s stability as it lets the product dry.
How Does Glycerin Work for Hair?
Glycerin, functioning as a humectant, possesses a commendable ability to bind and retain water. This characteristic arises from the presence of three hydroxy groups in its carbon chain.
Through hydrogen bonding, glycerin binds with water molecules, and the extent of this binding relies on osmotic pressure and humidity levels (availability of water molecules in the surrounding environment). This characteristic property is strategically utilized in various hair care formulations.
Humectants like propylene glycol, sodium lactate, and sodium PCA share similar characteristics.3-4 In products like shampoo, conditioner, leave-in conditioner, hair masks, or gel that contain glycerin, water molecules are attracted, elevating the hair’s moisture level.
The effectiveness of this moisture boost depends on factors like hair condition, protein level, porosity, damage, and external humidity. Notably, porous hair fibers, characterized by a larger cuticle layer pore size, allow higher moisture penetration into the hair structure.
Glycerin for Hair: Is it Good or Bad?
Water is crucial for your hair’s vitality, and while beneficial, glycerin can also have drawbacks. Its impact varies based on your hair’s condition and external weather conditions. Glycerin plays a significant role in improving hair moisture and combating dry hair and skin.
When hair becomes dry, it signals potential damage, leading to brittleness, loss of luster, and difficulties in styling and management.
The process of hair water uptake operates through a dynamic balance system, acting as a “Two Way Traffic.” Depending on the surrounding humidity, hair can either absorb or release water (desorption). Moderate water absorption is beneficial, enhancing hair health, quality, and appearance.
However, moderation is key. Excessive glycerin levels can lead to heightened water uptake, causing hair to swell and increase in diameter.
Too much moisture disrupts the hydrogen bonds of the keratin protein, especially under high humidity conditions, weakening the hair. Damaged hair, with higher porosity, is particularly susceptible to this issue, as it provides more space for water molecules to penetrate.
Individuals with pre-damaged hair should exercise caution and limit the use of glycerin products to prevent exacerbating these issues.
How to Use Glycerin for Hair Care
You can incorporate glycerin into your hair care regimen in a few different ways. Always do a patch test before widespread use to ensure compatibility with your skin. Here are a few examples:
- Add pure glycerin to your conditioner in a 1:5 ratio (if not already present).
- Use ingredients like egg, olive oil, and avocado, and apply a natural hair mask for 20-30 minutes.
- Apply glycerin directly as an oil treatment for 30 minutes before washing your hair.
- Mix it in a 1:1 ratio with a cup of water in a spray bottle for a nourishing hair spray.
- Get store-bought products containing glycerin, like hair mists and styling cremes.
The Disadvantages of Using Glycerin on Hair
Adverse effects or cons are usually present with any great product or ingredient. That also goes for glycerin. Here are some ways glycerin can negatively impact your hair strands:
- Excess or overuse use can lead to damaged hair.
- It can cause greasiness and build-up.
- Hair and scalp can become dry and flaky.
- It can make hair look weighed down.
- Overuse can lead to frizziness from excess moisture.
How Glycerin Affects Hair During Summer and Winter
Your hair responds to glycerin and behaves differently during summer and winter. The two seasons have different temperatures and humidity levels, and both factors influence the hygroscopic activity of glycerin.
During summer, glycerin is an excellent choice for hair hydration therapy, especially in dry climates. The humidity is generally around 50-65% RH level, making it beneficial for maintaining a balanced moisture level in the air.
A mixture of glycerin and natural ingredients, such as oils or butter, boosts the hair’s moisture content, lubricity, and tactile properties. The effect on curl definition may differ based on factors like humidity, styling products used, and your hair’s unique characteristics.
The best way that I’ve found to combat humidity during the summer months is to use a leave-in conditioner with the Advanced Climate Control Heat & Humidity Gel. This combination helps manage frizz and maintain your desired hairstyle, creating a barrier against humidity’s adverse effects.
During winter, the air is dry, with low temperatures and humidity. Frosty, windy conditions may also be present. Glycerin may not be a good option for your curls under these conditions.
It would attract water molecules inside the hair and scalp cells instead of drawing them from the air. This leads to increased water molecule loss from the hair surface, exacerbating dry scalp and hair.
Glycerin should be avoided in cold winter conditions (especially for curly and damaged hair). Emollients and oils are better for preserving the internal moisture level, lubricating the surface, and minimizing water loss.
Can glycerin be detrimental to hair with high porosity?
Hair with high porosity possesses larger pores in the cuticle layer, allowing increased moisture penetration into the hair structure. This can pose a challenge for high porosity hair, as it provides more room for water molecules to enter. You should be cautious and restrict the use of glycerin products to avoid worsening these concerns or consider using glycerin-free products.
At what point should I discontinue using glycerin in my hair care routine?
Consider limiting or discontinuing glycerin use if you observe excessive moisture absorption, especially in high humidity conditions, leading to hair swelling and weakening.
Can coconut oil and shea butter be used alongside glycerin in hair products, or do they counteract each other’s effects?
When combining coconut oil or shea butter with a glycerin-containing product, these emollients create a protective layer that reduces water loss from the hair. This layer acts as an “occlusive,” preventing water from easily moving in and out of the hair. However, the effectiveness may be impacted if other humectants in the same product compete with glycerin for water.
Does glycerin promote or hinder hair growth?
The impact of glycerin on hair growth varies. Glycerin can aid hair growth by maintaining hydration and preventing dryness, and split ends when applied to the hair. However, excessive use in dry climate conditions may lead to potential dryness and itchy scalp. Balancing glycerin-based products and considering climate and individual hair characteristics is crucial for optimal results.
What is Vegetable Glycerin?
Derived from vegetable oils, vegetable glycerin is a clear and sweet liquid. While glycerin can be sourced from animals, opting for vegetable glycerin provides a vegan-friendly alternative.
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.