A topic that we’re frequently asked about by consumers is about hair conditioning ingredients and which ones work best for different types of hair. While there is a lot of simple advice given, this is actually a complicated question with many different answers. For cosmetic formulators, it’s important to know all the options and the limits of our knowledge in answering this question.
Types of hair conditioning ingredients
In the book Conditioning Agents for Hair and Skin, the authors covered all the major types of conditioning agents. These include:
Why are conditioners used?
To understand how conditioning ingredients work, it’s helpful to know what hair problems conditioners are meant to solve in the first place. Hair conditioners have a few functions, but the main ones are:
- Making hair easier to comb
- Making hair feel better
- Protecting hair from future damage
- Making hair look better
How do conditioning ingredients work?
There are two main ways conditioning ingredients work. One way is by creating a film on the hair fiber surface. This makes the hair feel smoother when touched, reflects light better, and allows a comb to slide past more easily. The other way a conditioning ingredient might work is by penetrating the hair fiber. This helps make the fiber more flexible, which can improve manageability and reduce the chance of the fiber breaking. Some ingredients have the additional effect of attracting water to themselves, which can further improve the flexibility and feel of the hair.
Conditioning ingredients like lipids, silicones, cationic surfactants, and cationic polymers are all about depositing a water-resistant film. Humectants are more about penetrating and attracting water to the fiber.
But one thing that is true for any conditioning ingredient, it has to be left behind on the hair for it to work. Conditioning agents that wash down the drain are not doing anything useful for hair.
How do conditioning ingredients stay on hair?
There are a few ways:
Leave-on Products
The easiest and most efficient way to get a conditioning agent to stay on hair is to just spray or rub it on. This is how leave-in conditioner or hair mousses work. The downside of these products is that there may not be an even distribution of the product. There may be fibers or patches here and there that consumers miss. Plus, many people don’t like the extra step of having to spray something extra in their hair.
Rinse-off products
The most popular types of products are rinse-offs, including shampoos and conditioners. Of these, hair conditioners are much more effective in delivering conditioning ingredients. There are three main mechanisms by which conditioning agents stay on hair.
Hydrophobic Adsorption – Ingredients that are not soluble in water separate from the system during use and deposit on the hair fiber. These include materials such as silicones, lipids and emollients.
Electronegative Adsorption – These ingredients are more compatible with water; however, they have a positive charge which is attracted to negative charges on damaged hair fiber. This adsorption allows cationic surfactants and cationic polymers to stay behind on the hair and resist rinse off. It should be noted that cationic polymers can also follow the hydrophobic adsorption mechanism.
Diffusion Absorption – These ingredients absorb into the hair fiber, where they are shielded from the rinse water and will stay on the hair. Most materials will absorb into the hair a bit, but the time required is so long that the other mechanisms described above are more important. However, for water-soluble ingredients like humectants and proteins, this is the main way that they stay behind on hair.
Conditioning shampoos
While conditioners are designed to effectively deliver hair conditioning ingredients to hair, shampoos are mainly used to remove things from hair. This causes a problem for conditioning shampoos because they need to do the conflicting task of removing something while depositing something else.
So, most conditioning ingredients that rely on a hydrophobic mechanism to stay behind won’t work because shampoos are made to remove hydrophobic materials. This is why putting oils in shampoos makes little sense. This problem is further impacted by the fact that cationic materials are not compatible with the most common detergents in shampoos, anionic surfactants. So, cationic surfactants can’t be used either.
Ingredients that can last on hair through shampooing include silicones if incorporated properly in the formula and cationic polymers, which will still follow a dilution-deposition mechanism. These are inefficient products, so while a conditioning shampoo may be better than a standard shampoo in terms of conditioning, they don’t work nearly as well as a post-shampoo conditioner.
Why do some conditioners seem to work differently on different hair?
How well a conditioner works on hair depends on a couple of factors. This includes how damaged the hair is and how easily it absorbs ingredients. But it also depends on how a person feels.
Chemical reasons
If we consider conditioners work better if they reduce the force needed to comb, improve shine, and make hair feel better, then the following are true.
- Damaged sites: Hair that is more damaged will have more places on it where the cationic materials can bind. This type of hair may benefit from products that have a high level of cationic surfactants. Typically, longer chain (behenyl) conditioning ingredients will work better than shorter chains (cetyl); however, this can be evened out by using a higher level of a shorter chain ingredient.
- Penetration: More damaged hair may also benefit from humectants and penetrating oils since this type of hair is more permeable, and there is a greater opportunity for the ingredients to soak into the hair.
- Less damaged hair may benefit more from ingredients that don’t bind to hair at damaged sites, like oils and silicones. Of course, even damaged hair will benefit from these types of ingredients.
Wavy hair problems
Wavy or curled hair has added challenges. For example, its shape will be more prone to tangling. Its cuticle may lift up more at the turns. And it may not reflect light in a manner conducive to shine. So, this hair typically needs more conditioning ingredients to be left behind. But leaving too much behind on hair can make it weighed down and look drab or feel greasy.
Psychological reasons
One last point is that how a person’s hair looks and feels is also a result of how they feel at the time they are evaluating the results. In the lab, we may be able to demonstrate that conditioned wavy hair takes less combing force than unconditioned hair, but the consumer experience might not reflect the lab measured result.
A variety of things affect consumer perception, including fragrance, aesthetics of the formula, and even how they are feeling about life at the specific moment. And since everyone likes different fragrances and feels different at any moment, there is little a cosmetic formulator can do about this.
What ingredients are better?
Clearly, there is no simple answer to this question. Behenyl based ingredients may provide more slip than cetyl ingredients in a laboratory setting. But then they may feel like they weigh down the hair more, so the user doesn’t like it as much. This is the same for things like dimethicone or cationic polymers.
To formulate the “best” conditioner, you’ll need to spend time trying different ingredient combinations, combing tresses, and getting consumer feedback. And even then, it’s unlikely there is a perfect conditioner blend for everyone.
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I find all this info amazing as a heavy user of conditioners. I am chemist (PH D), formulate sunscreens and none hair products but enjoyed reading this article and will divulge this info.
Excellent breakdown of conditioner’s various functions, Perry. There is a “sweet spot” in making conditioning shampoo BARS where you are able to combine both anionics and cationics (as long as the bar is anhydrous) and have both function effectively, but it has taken me a lot of experimenting to successfully achieve this. I also would appreciate your opinion on non-quat cationics, and assuming these would fall into the category of Electronegative Adsorption ingredients? You also mention that “putting oils in shampoos makes little sense” and I question this theory as the effect an oil has depends much on its individual molecular size to determine whether it can penetrate or coat the strand, maybe you’d care to elaborate? Thank you.
Hi Perry,
Thank you for this article. Excellent as usual, as is all of your work. It is as good as ever. Do you sell your book Conditioning Agents for Hair and Skin through your website? I would love to get the book!
PS( my website below is under construction still!)
Dear Suzanne
Thank you for your comments. I agree theoretically you could combine anionics and cationics in a solid form and it would stay stable. Whether it will effectively condition hair while in the presence of water is something that could be tested. I suppose some cationic might stick to the hair but some also might combine to form an insoluble salt with the anionic. It would make for an interesting experiment. I’m skeptical it would perform in a way that appeals to consumers but it might.
For “non-quat cationics” I think that is marketing double-speak. In my opinion, these are Quats. The positive charge of the molecule is NH4+ That the nitrogen molecule comes from an amino acid doesn’t negate the fact that it is a quat. Perhaps you’re asking about something else? So yes, they would work via the same mechanism. Anyway, these quats may work just fine, but it’s unlikely they radically outperform industry standards like Cetrimonium Chloride or Behentrimonium Methosulfate. Standard ingredients have been used for a long time because they work, and they are inexpensive.
It’s fine to question the theory of the benefit of oils in shampoo. Here is my perspective. The main purpose of a shampoo is to remove oils. The way it does this is by using surfactants to surround oily materials (sebum), lift them off the surface, encase them in a micelle which can then be rinsed away. If you incorporate an oil into a shampoo and it stays stable, that means it’s already been encased in a micelle. When you put the product on your hair for it to work it would have to break free from the micelle it is already in, then get to the hair surface and penetrate before it gets trapped up by all the other surfactant micelles that are forming and removing oil. I haven’t done the mathematical modeling of the system but my guess is that the oil already tied up in micelles in your formula is mostly just going to be rinsed down the drain before it ever has a chance to penetrate the hair. And it will also certainly reduce the foaming properties of your hair.
Of course, I could be mistaken. I could imagine an experiment which would show indeed a significant amount penetrates the hair. I just haven’t seen it.
Regards
Perry, 44