The Humectant Glycerin
Glycerin has been a FAQ when it comes to hair care products, so I wanted to do a brief post to cover it. If you want more in depth information about humectants, please see my blog on ‘Dew Point, Humectants, and Humidity’.
Glycerin is an alcohol also known as glycerol and 1,2,3, propane triol. It is a small molecule, which simply means that there are not a lot of places on the molecule to bind water. Glycerin is one of the humectants that gains and loses moisture readily. Other humectants that behave similar to glycerin are propylene glycol, sorbitol, agave nectar, and honey.
Why is Glycerin Beneficial to Hair?
According to John Davis, Co-founder and Director of AG Hair Cosmetics,
“We use it mainly for moisture retention in the product and the hair and skin. With regard to curly hair, hair is comprised of protein, and having more moisture helps to maintain curl in the hair. It helps to encourage curl.” Dr. Ali D. Ghannad, vice president of research and development for Farouk Systems agrees. “If I have a product that is thick and I need to put something to decrease the viscosity or thickness, I may use glycerin because it doesn’t hurt my product but helps by being moisturizing. If you use too much, though, your hair becomes tacky or sticky.”
According to Wendy, Hair Scientist,
“Humectants attract water to themselves. Humectants like glycerin are great at grabbing water vapor out of the air. When you have a hair gel with glycerin in it, when there is ample water in the air (humidity) - the air is going to be hydrating the glycerin in the product, which is going to help your hair stay hydrated. Well-hydrated hair has more bounce and definition. A second benefit of glycerin in products (when there is ample water vapor in the air) is that glycerin keeps hold-providing ingredients that would otherwise create a brittle, candy-like finish from feeling brittle and candy-like. Glycerin (and sorbitol and propylene glycol) take water vapor from the air to hydrate the dry gel in your hair and keep it more flexible. When there isn't enough water vapor in the air (low humidity and/or low dew points), the gel loses that benefit from the glycerin and the gel becomes more brittle, creates friction and that means hair that feels dry and crusty and looks dull.”
When the air is very dry, glycerin is a much less effective ingredient. When the humidity is just right, glycerin can help your hair look and feel great. When the weather gets too dry, glycerin can't pull enough water to itself and it loses its effectiveness. When the air is very humid, glycerin tends to pull a lot of water in, which means- poof, your hair loses definition.
Things to Consider When Using Products with Glycerin
Before you decide to give up on products with glycerin, know that a lot of how ingredients, like glycerin behave, depends on the FORMULA of a product as a whole. It all comes down to trial and error...as usual.
Sometimes formulations are a problem because it uses only glycerin as a humectant and without emollients or film forming humectants. Well balanced products avoid this pitfall. There are also some other ingredients that can leave a strange feel in hair or create frizz, but usually the formula as a whole determines whether this or that ingredient is a problem.
I think it’s more than an issue of weather and glycerin. For example, consider what other products you use in your hair. If you were to combine oil, or conditioning ingredients found in leave-in conditioners, curl creams under a glycerin containing product, that may help combat the glycerin issue because they will combine to actively attract, hold water, and slow water loss.
If you used oil or leave-in conditioner under a glycerin-containing product, that layer of emollients would slow down water loss from hair. If there are other humectants that are not a ready to give up their water as glycerin in the same product, the effect might be reduced. Oils and conditioners act as "occlusives" - the layer of oil or leave-in conditioner is not water-soluble and that helps slow the movement of water in and out of hair.
Some plant extracts are made in a water and glycerin base, some are not. Most plant extracts are used at around 1%, so if the base was 50% glycerin, the total amount of glycerin added to the product by that plant extract might be 0.5% - which is not much, but enough to have a humectant effect. Product labels are not required to include components like glycerin or preservatives in their plant additives, so this is not information you will find on a product label.
If you want to eliminate all "humidity” humectants for a while- focus on glycerin, sorbitol, propylene glycol, agave nectar, or honey. Note: not all of them may be a problem.
If glycerin is further down the ingredients list, I don’t think you have to worry too much about the dew points.
Sometimes glycerin is used as a thickening agent in many products to create a nice full texture.
A milder humectant may be used in conjunction with a stronger one in the formula to create some sort of balance, so again, it’s all about the formula as a whole.
Here are other humectants that may work better for your hair in all weather for maintaining moisture:
Amino acids and Protein
Note: These are less like glycerin and slow down water loss from inside the hair.
Leave me a comment and let me know if this was helpful. Thank you!