Last Updated on April 12, 2023 by Verna Meachum

You know that feeling when your hair just won’t cooperate? You’ve tried every styling product under the sun, but your locks still look like a frizzy mess.

If you’re dealing with humidity, the answer might be to use a humectant or an anti-humectant.

But what’s the difference between these two types of ingredients? And when should you use them?

Read on to find out!

Introduction

Humectants are cosmetic ingredients that can absorb and hold water molecules.¹ Anti-humectants are the opposite of this; they are chemical agents that can block the binding or absorption of water molecules.

These two technical terms are frequently discussed among curly hair care consumers. They represent two completely different classes of chemical ingredients that work in opposite directions and follow different mechanisms.

A typical example of a humectant is ‘Glycerin,’ while natural oils, butter e.g. Shea Butter are anti-humectants.

Both are commonly used in hair care formulations to control water molecules binding with hair fiber.

Defining Humectant vs Anti Humectant

A humectant is a chemical compound having the ability to absorb, bind and hold water molecules.

Anti humectant is the opposite, it is a chemical compound that can block or prevent binding or absorption of water molecules.

Humectants are also called hygroscopic. Their water absorption or holding capacity varies with their chemical structure as well as external weather conditions.²

Opposite to this, anti humectants act as a lubricant and occlusive agent preventing access of water molecules to the substrate (e.g. hair surface).

So, why are humectants and anti humectants important to curly hair care consumers? And how should they be used?

First, let’s make a list of both humectant and anti-humectant commonly found in hair care formulations

Humectants

Here, humectants are further classified into two groups, small molecules and large molecules highlighting their molecular size and ability to penetrate.

Humectant	Molecule size
Glycerin	Small molecule
Propylene Glycol	Small molecule
Sorbitol	Small molecule
Sodium PCA	Small molecule
D-Panthenol	Small molecule
Sugar based molecules e.g. glucose, lactose	Small molecule
Acetamide MEA	Small molecule
Sodium Lactate	Small molecule
Polyethylene glycol – 200	Large polymeric molecule
Hyaluronic acid and its salt	Large molecule
Proteins, peptides	Large molecule
Amino acids	Small molecule
Aloe Vera derived compounds	Large Molecule

Anti humectants

• Plant sourced butter, e.g. Shea Butter, Mango Butter, Cocoa Butter etc.

• Plant oils, e.g. Olive Oil, Sunflower Oil, Rapeseed Oil etc.

• Natural waxes e.g. Beeswax

• Lanoline and lanolin derivatives

• Synthetic esters, e.g. C12-C15 Alkyl Benzoate, Isopropyl Myristate, etc.

• Silicones, e.g. Dimethicone, Cyclomethicone, amodimethicone, etc.

• Petroleum sourced e.g. petrolatum, petroleum jelly, mineral oil

Balanced Moisture is Key

We all know that hair requires moisture in order to have a naturally beautiful appearance, and we understand that water is the critical and essential ingredient for hair health.³

Hair that is dry, damaged, porous, and susceptible to breakage can be caused by regular maintenance (everyday grooming) and harsh chemical treatments. To address these concerns, formulations often contain humectants or other moisturizing agents to maintain hair water level.⁴

Anything above what is necessary is bad, in other words – anything in excess is bad. A balance should be sought at all times; if the water content in your hair is too low, it will be dry and brittle.

On the other hand, if there is too much water content, it will damage your hair.

Curly hair and water content

Curly hairs are unique due to their special structural features and characteristics.

Water content that is too low or excessive can be damaging and make styling and maintaining curl definition difficult.

For instance, applying too much humectant can draw a large number of water molecules into the curly hair shaft causing severe water pressure inside the fiber structure.

Hair undergoes significant swelling and under extreme conditions, it may even cause lateral cracks along the hair length.

Hair in that condition needs anti-humectants. They work opposite to humectants by preventing water–hair binding. They form a delicate water-resistant film on the hair shaft and hence block water binding to the hair protein sites.

This blocks excessive water pressure and thus controls hair water content. That’s how they preserve the natural physicochemical properties of curly hair.

Frizz and Anti Humectant

Frizz is another major problem for curly hair. Hair appears misaligned with a poor curl pattern where each fiber has its own alignment or curl pattern.

The ends of the hair point in all sorts of directions, creating a messy and unorganized appearance.

High humidity and wet weather conditions or frequent washing are the main reasons for this problem.

To fix the problem, you must first control and minimize hair exposure to extremely wet weather and high humidity levels for an extended period.

Anti-humectants can help by blocking the absorption of water by hair proteins, thus preventing frizz.

Natural oils or butter do this job amazingly and hence are the quick remedy for curly hair frizz.

Humectant vs Anti humectant: How to make them work during extreme humidity conditions

Let’s work out two extreme humidity conditions, high humidity, and low humidity.

Humidity > 80%

High humidity means the surrounding air is saturated with moisture and a large number of water molecules are available.

Hair can absorb moisture from the surroundings and increases in weight and swells; this causes frizz.

Under these conditions, anti-humectants or moisture blockers are needed.  

Humidity 55-65% (moderate level)

At this humidity level, hair tends to maintain a balance and it needs both humectant and anti-humectant to maintain this balance.

Applying too much of either one can affect the hair quality. Hair needs a balanced formulation having both humectants as well as natural oils or butter (or proteins).

Keep your curls clean and regularly apply moisturizing conditioner.

Humidity < 40%

Low humidity means air is dry and does not contain many water molecules. Hair tends to undergo desorption losing water molecules.

As water molecules leave, hair becomes dry, brittle, and rigid. Hair proteins lose their natural texture and it does not feel soft and smooth.

At this stage, the strategy is to control water desorption. Applying an anti-humectant can prevent this water loss.

Takeaway and Key Steps

·      Humectants and anti-humectants are opposite each other.

·      Humectants absorb water while anti-humectants block water absorption.

·      Humidity and outside weather conditions are vital when deciding whether your curls need humectants or anti-humectants.

·      Keeps your curls clean.

·      Always apply a balanced conditioning formulation having both humectants (e.g. glycerin or propylene glycol) and anti-humectants (oils or butter).

·      Keep an eye on weather conditions and alter your curl care regimen accordingly.

·      Remember: Too much of anything is bad. Maintain a healthy balance.

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References

1. Schueller, R.; Romanowski, P., Conditioning Agents for Hair and Skin. Taylor & Francis: 1999.
2. Christoph, R.; Schmidt, B.; Steinberner, U.; Dilla, W.; Karinen, R., Glycerol. In Ullmann’s Encyclopedia of Industrial Chemistry, John Wiley & Sons: 2003.
3. Marsh, J. M.; Gray, J.; Tosti, A., Healthy Hair. Springer International Publishing: 2015.
4. Zviak, C., The Science of Hair Care. Taylor & Francis: 1986.