The Science of Hair: Why Your Go To Hair Products Stop Working

August 18, 2022


Verna Meachum

Learn why your go to hair products stop working.

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Last Updated on April 9, 2023 by Verna Meachum

Welcome to the club, curly friends. We’ve all been there. You finally find the perfect styling product or conditioner and it gives you the shiny, defined ringlets you’ve always wanted.

But then, seemingly overnight, your hair products stop working. Your curls turn into frizz and your hair feels like straw.

What could have gone wrong? The unanimous answer is that the product has stopped working. But is that really what’s going on?

The truth is, there are many reasons why a product might not be giving you the same results as it once did.

Product build up, hormonal changes, environmental damage and even the weather can all cause a product to stop working its magic.

So don’t give up on your favorite products yet! There are ways to counteract these problems and get your hair looking and feeling amazing again.

Stay tuned for our tips on how to revive over-the-hill products.

Does Hair Build Tolerance And Cause Hair Products To Stop Working?

Have you ever noticed that your hair seems to get used to products over time? Or no longer responds to your go-to products the way it used to?

Have you ever heard that your hair “build immunity” to certain hair care products over time?

You’re not alone. We’ve all been there. The truth is, hair does not build immunity or tolerance to hair products.

Let’s start by defining the phrases “hair tolerance” and “hair immunity.”

The terms, “Hair Tolerance” or “Hair Immunity” to hair care products are confusing and misused, and often used interchangeably. In general, they refer to the idea that hair gets used to products over time, so that the products stop working as well as they did in the beginning.

There are a few things to unpack here.

First, hair cannot build immunity or tolerance to hair products in the same way that our bodies can to things like diseases or allergies.

Second, hair does not get used to products in the sense that it becomes resistant to their effects. So, if hair doesn’t build immunity or tolerance to hair products, what’s really going on?

The questions are;

  • Is it appropriate to use ‘tolerance” or “immunity” to describe this issue?
  • Is it scientific or just a myth?
  • What is the problem with hair and why are they not responding to your go-to shampoo or conditioner anymore?

Scientific terms: Tolerance, Immunity, or Hair Response

‘Tolerance” in science means the capacity of a substance to endure a situation or treatment. On the other hand, immunity is a commonly used term in biological sciences highlighting the ability of a subject to resist a particular situation (disease, toxin, etc.).

Hair is a protein fiber that emerges as an outgrowth from hair follicles on the scalp surface. It is a dead outgrowth just like nails or horns.

Hair does not contain any living cells or other living organelles and does not breathe. Hence, it does not work like our other body organs e.g. skin, heart, or kidney.

It is not appropriate to use the purely biological term, immunity for hair. The fact is, hair does not develop any immunity against any drug, chemical, or even cosmetic products.

Likewise, it does not have tolerance for any particular treatment. Therefore, it is not scientific to use the terms, “Hair Immunity” or “Hair Tolerance”.

While it is true that your go to products can stop working for your hair, however, the terms “hair immunity or hair tolerance” are a misrepresentation of this observation.

“Hair Unresponsive” perhaps is a more precise and accurate term, referring to a zero response from the hair upon applying a hair care product.

Why is it that hair products produce little-to-no results, even when used regularly? Why is it not working anymore? What has changed?

Why your go-to shampoo and conditioner stop responding

Hair is a protein-made fiber that have pores on its surface across the cuticle layer. These pores allow the absorption of substances applied to it.

For example, hair absorbs a significant amount of water, even from the air during high humidity conditions.

With hair care products, functional active ingredients either stick to their surface via electrostatic bonding or penetrate deep inside the hair cortex.

Cationic polymers and softeners show more adhesion and penetration due to their positive charge density as they bind with negative sites of protein amino acids of the hair fiber.1

Excess of anything is bad and it is the same with hair care products. Using too much hair product or repeated application of the same product for a good amount of time can lead to hair product build up on the hair shaft with significant changes in its morphology and surface properties.

Build up

Build up from hair products can be described as a hair shaft that is unable to function or “breathe” properly because it is coated with a layer of residue. This explains why your hair might need a break from certain products after using them for a while.

However, there are a few reasons why your hair might seem like it’s no longer responding to your products.

Hair care formulations quite often contain natural or synthetic polymers having a large molecular size and molecular weight.

Functionalized polymers e.g. guar Hydroxypropyltrimonium chloride or polyquaternium-7 or polyquaternium-10 are commonly used in shampoos and conditioners.

The drawback of using these ingredients is their build up effect on the hair surface. The build up is a fine coating of these materials over the hair surface which eventually may hinder the penetration of water and other active ingredients into the hair cortex.

Moreover, the polymeric coating increases hair stiffness and hair may become slightly rigid. This alters the physical and chemical properties of hair and hair may become unresponsive to the hair care products. 2

Weather conditions

Hair is different in different weather conditions. It is affected greatly by changing temperature and humidity levels.

Being a porous material, it can absorb moisture from the surroundings. During wet conditions, humidity is high, the air is saturated with water molecules and thus hair absorbs water and swells in diameter.

In contrast, during dry winter times, the air is dry, humidity is low and thus, hair desorbs water molecules (water molecules leave hair fiber) making hair even drier.

Therefore, hair needs different hair care formulations for different weather conditions. The same shampoo and conditioner may not work for all seasons and climate conditions.

Changes in hair chemistry

Another key factor causing hair unresponsive is changes in its chemistry. Natural (virgin, non-chemically treated) hair fiber is different from chemically treated hair fibers.

For example, oxidative hair bleaching changes the protein content of hair; bleached hairs are more porous and fragile due to protein loss.

A chemical change to your hair alters the natural composition and, as a result, may not work with the same products you used before. You might need a new custom formulation specifically for chemically-treated hair.

What should we do?

Now that we have cleared up the confusion in regards to “hair tolerance” and “hair immunity” to hair care products, we’re left with one final question, what should we do?

The first step is to be aware of the causes that make hair unresponsive to hair care products. Once you identify the cause, you can take steps to mitigate it.

Remove build up

Regularly use an anti-residue shampoo to remove any build up on hair. It will ensure the hair surface is clean and fresh.

It should be followed by a good moisturizing shampoo and conditioner to provide a balanced hair care treatment.

Anti-residue or clarifying shampoo should be a green, sulfate-free formulation and should not strip off hair’s natural lipids.

Protect hair against weather changes

Use a customized approach for your hair care routine with changing weather conditions. During winter, the air is dry and this draws moisture from the hair shaft.

As a result, hair becomes dry, brittle, and lacks life. Use a more moisturizing formulation containing a good blend of emollients and natural oils.

Anti-frizz ingredients are highly recommended to combat the frizz problem. It is vital because continuous exposure to frosty winter can even break the hair ends causing “split ends“.

During summer, protect hair from harsh solar radiation as extended UV exposure can cause significant hair damage. It is strongly advised to use a solar protector for outdoor activities.3


1.  Zviak, C., The Science of Hair Care. Taylor & Francis: 1986.
2.  Marsh, J. M.; Gray, J.; Tosti, A., Healthy Hair. Springer International Publishing: 2015.
3.  Nogueira, A. C. S.; Dicelio, L. E.; Joekes, I., About photo-damage of human hair. Photochem. Photobiol. Sci. 2006, 5 (2), 165-169.


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