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Protein; How it Relates to Porosity and How to Use it

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Verna Meachum

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Protein is important for hair health, but it can be tricky to use in different hair types because of its relationship with porosity. For instance, using protein on coarse/kinky curly and other tightly coiled textures may result in: dryness; breakage; flakiness; product build-up (i.e. product residue); and/or a dull appearance.

Using the right amount of protein is a good first step to prevent any potential issues.

Hair Protein

Hair is a protein fiber which is known as “keratin”. Predominantly two-third of hair mass is composed of keratin. All proteins are made up of small repeated building blocks called amino acids. As the name denotes, an amino acid is a chemical compound containing an acidic, as well as a basic group, in the same molecule.

The quite fascinating aspect is that there are twenty amino acids in nature and all proteins are made up of these 20 amino acids in different combinations. These amino acids are monomers that combine in various combining patterns to make thousands of proteins in living bodies.

Figure 1: A basic amino acid structure

Amino acid analysis of keratin has revealed its chemical composition, and sulfur-rich cystine is the main component of keratin. This cystine is the backbone of hair structure as it is involved in disulfide linkage in the keratin helical structure (Fig 2).

This disulfide bond is the one mainly responsible for the mechanical strength of hair fiber and also subject to various chemical treatments. For example, in bleaching, hydrogen peroxide can break the disulfide bond and generate hydrophilic cystic acid that results in decreasing the mechanical strength of hair fiber. Hair becomes weak and fragile.

Figure 2: Chemical structure of human hair. It shows various chemical bonds and mainly disulfide bond (-S – S -).

How Chemical Treatments Damage Our Hair –  Protein Loss

The mechanical strength of hair is important because it prevents hair breakage. Various studies have concluded that the same hairs before and after a chemical treatment have a different total protein content. Among the different cosmetic treatments, hair bleaching using alkaline hydrogen peroxide cause the most hair damage. Besides the decolorization of melanin pigment, hydrogen peroxide degrades hair protein.

Hydrogen peroxide can attack the disulfide bond of hair and break it. This chemical change converts cystine amino acid into a more water-soluble derivative called cystic acid. As a result, the overall amount of cystine in hair decreases while the total amount of cystic acid increases significantly (see photo below).


Cystic acid is more water-soluble and its presence at the hair shaft makes hair brittle, rough, and more hydrophilic (water-loving). This will result in hair having more frizz, and hair will become more difficult to manage.

Figure 3: Increase in cystic acid level with increasing bleaching strength.3

What is Porosity?

Porosity is the presence of pores on a substance. In scientific terms, “porosity is the ability of a material to have pores” and such a material is called “porous”. Pores represent a space where something can be absorbed, stored, or can pass through. In other words, Porosity refers to the hair’s ability or inability to absorb water or chemicals into the cortex. All hair is naturally porous and permeable to water, BUT only to the degree of porosity and will vary by the individual, and the condition and shape of the hair’s cuticle layers. Porosity is generally categorized as high, medium, or low porosity.

Your hair porosity can change, depending on what’s done to it. Hair can be damaged by harsh chemical treatments such as perms, bleach, oxidation colors. It can also be damaged by mechanical styling, blow-drying, and simple wear and tear (it’s not uncommon to have highly porous ends, as they are the oldest part of your hair). (1)

What happens to hair during these treatments or applications? These type of treatments attack the hair’s protein structure and its protective cuticle layer becomes damaged or impaired, causing them to lift or separate, which can also create gaps between your cuticles and, as a result, your hair may be more porous than it would normally be. Hair in this condition is said to be porous.

Understand that high porosity hair can be genetic and it does not necessarily mean that it is the result of damage.
For example, ceramic pans can absorb plenty of water, and gas can pass through them easily. Similarly, hair being a natural material, has numerous pores, and can uptake a good amount of water. Ever wondered why your hair gets weighed down as it gets wet? The reason is the absorption of water molecules by small tiny pores present along the hair shaft.

Natural untreated virgin hair can gain up to 30% increase in its original weight by absorbing moisture. (4) Another example is the dye uptake during hair coloring. Small dye molecules penetrate the hair and are trapped in small empty spaces in the cuticle and cortex. Similarly, various conditioning agents are also found inside hair after a conditioning treatment under the microscope. Interestingly, hair porosity can increase significantly by harsh chemical treatments.

Bleaching, perms, and hair straightening treatments may increase the pore size, its volume, and geometrical dimension that leads to an increase in the overall absorption capacity of hair. Bleaching hair with 30 volumes of alkaline hydrogen peroxide is a worst-case scenario where it can increase porosity by a factor of more than two times.

What causes an increase in the pore size? Studies show that due to harsh chemical treatments, small tiny pores naturally present along the hair shaft open up. Degradation of protein material causes dilation of existing pores and may even merge two dilated or enlarged pores together, increasing the overall pore size and volume. (5)

Figure 5: Increase in pore size as a result of hair bleaching.5


The porosity is directly related to hair mechanical strength. The higher the porosity, the lower the mechanical strength of hair. Thus, highly porous means, hair is fragile, damaged, and can even break during combing or daily grooming.

So far, we can say highly porous hair has low mechanical strength which is, in turn, due to protein loss. Thus, highly porous is a serious danger to hair health and its overall look. So, what can we do to minimize or correct damage?

The Role of Protein Treatments

The prevailing problem with porous hair is the issue of raised cuticles. If you can “close” the cuticle layers, even a little, you will resolve a majority of your porosity issues. Conditioning agents are employed in hair care products to prevent or improve hair quality. Oils and butters such as coconut, argan, castor, and shea butter have been in use for decades.

Silicones conditioners are also commonly added to products as they offer slip and shine. An important class of conditioners is protein or protein derivatives. Vegetal or animal sources proteins are available along with their hydrolyzed or hydrophobic versions. These days, consumers prefer plant-sourced ingredients and that’s why proteins extracted from plants or plant seeds are more in demand.

A well-known example is hydrolyzed wheat protein. Similarly, soya, oat, and rice extracted proteins are used in hair care products. Their molecular weight and size vary significantly and depend upon the method of preparation and thus varies among the manufacturers.

Proteins improve hair quality by penetrating the hair, aligning its cuticles, and filling the empty pores inside the cortex. They can also coat the hair’s surface forming a thin protective film. Results have shown that protein treatments containing large amounts of proteins boost hair shine and reduce fiber to fiber friction. This results in minimizing hair porosity and improving hair sheen.

Proteins We Commonly Find in Hair Care Products

Vegetable derived proteins are preferred due to their sustainability and biodegradability. Their performance depends upon the source they are extracted from, their molecular weight/size, and solubility in water. Smaller molecules have a better chance of penetrating the hair and this is true for proteins as well. (6) Different proteins extracted from different sources have different amino acid compositions. Some examples are listed in the table below with their average molecular weights.

What Does the Molecule Weight of Protein Tell Us?

Choosing a protein depends upon its molecular weight to achieve your desired results. In the above table, we have the average molecular weights for commonly used proteins. Low molecular weight proteins can penetrate the hair and can go deep into the cortex and hence is desired more for deep hair treatment. They can strengthen the hair fiber and recover protein loss as a result of harsh grooming and chemical treatments.

However, high molecular weight proteins get adsorbed (coating) at the surface of the hair shaft. They show good adsorption at the cuticle layer and greatly improve their surface features. This gives great shine and ease of combing for wet and dry hair.

Various proteins are available on the market that can deliver excellent hair conditioning. The basic details for some selected proteins are provided below.

a. Keratin

Keratin is one of the most abundantly used protein ingredient in hair care products. The main reason for its high demand is basically the theory of “like, alikes”. As hair itself is made up of keratin, it has preference for same (alike) molecules. Primarily keratin is extracted from wool which is subsequently purified, fractionated, and may be modified for its cosmetics applications. Hydrolyzed versions are rich in cystine, and thus have attracted much attention from formulators and consumers. Its addition in chemical treatments (bleaching, dyeing, or perms) improves hair sensorial features both at the wet and dry stages.

b. Collagen

Collagen was probably the first protein ingredient ever used in hair and skin care products. This magic material has immense water binding capacity and that’s why it is used for dry and brittle hair. It delivers great moisturization and hydration to the hair surface without any static charge generation.

Low molecular weight collagen (500 – 1000 Daltons) is desired for penetration where hair strength is required.

Higher molecular weight collagen (>2000 daltons) is required for coating (adsorption) and improving the hair surface properties such as cuticle alignment, shine, combing, and brushing. It is available as a dry powder or water solution and is easy to incorporate into rinse-off or leave-on products.

c. Wheat protein

Wheat protein is rich in cystine and this offers an extra benefit. Various studies have found it to be an effective ingredient when added in hair bleach, perms, and straightening products. It reduces hair brittleness and frizz and helps in controlling hair damage.

d. Oat protein

Oat protein also improves hair shine and can repair hair damage. It contains higher levels of aspartic and glutamic amino acids which potentially play important role in hair moisturizing and hydration. Interestingly, it also minimizes the irritation potential of other chemical ingredients used in shampoo or conditioner formulations.

e. Silk protein

Silk protein is a low molecular weight protein (300 – 700 daltons) with a small molecular size. It exhibits excellent water-binding properties. It provides silk, smooth and superb moisture to dry and damaged hair.

f. Rice protein

Rice protein (molecular weight 1000 – 3000 daltons) enhances moisturization and tensile strength of hair. Interestingly, it raises hair volume when added in leave-on products. It is believed to be due to adsorption and strong film formation at the surface.

g. Milk protein

Milk protein is also a small molecular size (molecular weight 500 – 1500 daltons). It is a popular choice for moisture retention and film coating at the hair surface.

h. Corn protein

Corn protein has a small-medium molecular size that enhances hair conditioning, hydration, and detangling. The amino acid composition reveals it has high levels of glutamic acid that is responsible for its moisturizing properties.

i. Quinoa protein

Quinoa is a magic grain that is rich in protein. In fact, it contains highest level of protein among all other grains. That’s why it has been gaining popularity as a “master food”.

Recently, its hydrolyzed aqueous proteins have been added to hair care products. It offers smooth film formation along the hair shaft along with moisture retention and hair damage repair and control.

j. Sweet almond protein

Hydrolyzed almond protein has an average molecular weight of 2000 – 5000 daltons, and is rich in nitrogen. It offers unique sensorial features when applied in hair care treatments. Just like almond oil, hydrolyzed almond protein has a special composition of amino acids that coat the hair’s surface very efficiently. Interestingly, this protein also contains some starch hydrosylates which are believed to responsible for these extra benefits.

k. Jojoba proteins

Jojoba derivatives are well-known in hair care products. Recently, a new addition is jojoba proteins. It is an ideal film-forming protein due to its higher molecular weight molecular as well as high nitrogen content to provide excellent conditioning.

l. Recent advances having silicone modified protein derivatives

Recently, we have seen a new generation of vegetal proteins that have demonstrated remarkable properties in controlling hair porosity. Quaternized proteins containing positively charged nitrogen group offers high substantivity to negative charges (for example, cystic acid) present along the hair shaft leading to improved hair detangling and conditioning.

Hydrophobic proteins having a long silicone chain attached are also available. They are typically used in hair treatment products to prevent hair breakage and improve hair mechanical strength. These new versions are gaining popularity among formulators because of their superior conditioning properties.

Who Should Use Proteins?

Using chemical treatments for hair is not old news. Some of us (at one time or another) have had our hair bleached/lightened, permed, or straightened. This means, some of us have had damaged hair and needed some type of advanced (or emergency) hair treatment.

Protein treatments are the best options for these damaged hairs. In summary, we should say, use deep protein treatment if you have;

• Bleached hair

• Oxidative coloring

• Perms

• Relaxers (lye or no-lye) and other hair straightener products

• Too many brushing or weather and blow drying

• Excessive use of flat irons and other thermal hair styling

• Split ends (use protein on the ends of your hair)

• After swimming or pool bath (damage by chlorinated water)/Overexposure to salt water

• Sun damage (Exposure to UV radiations)

• Over washing hair with strong detergents

How Should We Use Protein?

This is an important question because we need to make sure; we get the maximum benefit out of added proteins to our regimen. Here is a simple step-by-step procedure to achieve your desired results. This is only meant for highly damaged, dry, and frizzy hair.

• Wash your hair with a residue removal shampoo, rinse it off thoroughly

• Remove excess water

• Apply a deep protein treatment that contains low molecular weight proteins (e.g. collagen, wheat, oat, or milk), work it through your hair using a wide comb, or your fingers.

• Leave it for 15-20 minutes (if the weather is cold in your area, you may use your blow dryer to warm it up a little). Warming it up will help to accelerate or ease penetration.

• Cover it with a plastic cap (or whatever you have on hand)

• Rinse off your hair thoroughly with warm water and apply a protein conditioner having high molecular weight proteins (e.g. sweet almond or jojoba proteins).

• Understand that in the first step, we used a low molecular weight protein to make sure it penetrates deep and fills in the empty pores of the hair shaft. With a light conditioner having higher molecular weight proteins – we are sealing and coating. This will trap conditioner molecules inside the hair.

• You can use this strategy every 10 days. During that period, use protein shampoo and light conditioners.

Note: Because low pH products and treatments bring about cuticle “closure”, some porosity problems can be temporarily resolved by applying a low pH solution or product. An apple cider vinegar rinse or even a simply cleansing with a neutralizing shampoo can help correct a porosity problem and help tighten and “close” the cuticle layers.

Important Cautionary Measure

Excess of everything is bad. Excessive use of high molecular weight proteins will cause build-up on the hair, which will make the hair dull, heavy, and no shine. If this happens, you need to stop using protein treatments and wash your hair with anti-residue shampoo. I advise you to use protein treatments only every 10-15 days and after the treatment, use a light shampoo having naturally derived mild surfactants followed by a light conditioner.

Final Words

Highly porous means hair is damaged due to protein loss. Porous hairs are difficult to style and manage. To control, repair, or recover this loss, protein treatments are a great remedy. The addition of proteins in our shampoo, conditioner, or leave-on products can significantly recover highly porous hair and enhance its overall health. Small protein molecules penetrate and coat the hair’s surface forming a thin film that enhances the surface alignment, shine, and reduces fiber to fiber friction.


1. Robbins, C.; Kamath, Y., Hair breakage during combing. IV. Brushing and combing hair. J. Cosmet. Sci. 2007, 58 (6), 629-636.

2. Bhushan, B., Biophysics of Human Hair: Structural, Nanomechanical, and Nanotribological Studies. Springer Berlin Heidelberg: 2010.

3. Grosvenor, A. J.; Deb‐Choudhury, S.; Middlewood, P. G.; Thomas, A.; Lee, E.; Vernon, J. A.; Woods, J. L.; Taylor, C.; Bell, F. I.; Clerens, S., The physical and chemical disruption of human hair after bleaching–studies by transmission electron microscopy and redox proteomics. Inter. J. of Cosmet. Sci 2018, 40 (6), 536-548.

4. Syed, A. N.; Ayoub, H., Correlating porosity and tensile strength of chemically modified hair. Cosmetics and toiletries 2002, 117 (11), 57-64.

5. Hessefort, Y. Z.; Holland, B. T.; Cloud, R. W., True porosity measurement of hair: a new way to study hair damage mechanisms. J. Cosmet. Sci. 2008, 59 (4), 303.

6. Schueller, R.; Romanowski, P., Conditioning Agents for Hair and Skin. Taylor & Francis: 1999.

Further reading:

Zviak, C., The Science of Hair Care. Taylor & Francis: 2005

Marsh, J. M.; Gray, J.; Tosti, A., Healthy Hair. Springer International Publishing: 2015

Robbins, C. R., Chemical and physical behavior of human hair. 5th ed.; Springer: 2012

Johnson, D. H., Hair and Hair Care. Taylor & Francis: 1997.

Scientific literature review: Hydrolyzed Source Proteins as Used in Cosmetics 2012.

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