What is Protein?
Proteins in our hair, specifically keratin, consist of amino acids, which are the fundamental building blocks of protein molecules. Amino acids are chemical compounds that contain both an acidic and a basic group within the same molecule.
The primary component of keratin is cystine, a sulfur-rich amino acid. Cystine plays a crucial role in the structure of hair, as it forms disulfide linkages within the helical structure of keratin. These disulfide bonds are primarily responsible for the mechanical strength and resilience of the hair fiber.
So, long story short, protein is what makes your hair strong.
What does the protein in hair products do?
Exposure to heat, chemicals, and environmental stress can lead to the weakening of disulfide bonds in our hair. Consequently, the cystine amino acid undergoes a conversion into a water-soluble derivative known as cystic acid. This conversion reduces the amount of cystine present in the hair while significantly increasing the concentration of cystic acid. The presence of cystic acid on the hair shaft causes it to become brittle, rough, and more prone to absorbing water (hydrophilic). This degradation of protein structure leads to higher hair porosity, increased frizz, and greater difficulty in managing the hair.
Proteins in hair products are designed to replace the eroded protein in your hair by coating, filming, or reinforcing the individual strands. They work by penetrating the hair, aligning its cuticles, and filling the empty pores inside the cortex. However, not all proteins can effectively accomplish this goal.
The molecular weight of proteins plays a crucial role in their absorption into the hair. Proteins with a molecular weight of 1000 daltons or less are considered ideal as they are weakly cationic and can form the best bonds with the hair. On the other hand, proteins with large molecular sizes, such as those found in whole foods, may not provide long-lasting benefits to the hair when applied directly. For instance, applying a whole egg to the hair may not effectively replace lost proteins in the long run.
pH is also a factor. Proteins bond well to the hair when they are found in products between a pH of 4 and 7, with 5 or 6 being the most effective.
And, finally, if you have hair that is fine in diameter, generally speaking, a medium to large protein can give you the strengthening and conditioning effects you are looking for. If your hair is more coarse, smaller proteins are more effective. And speaking of diameter, fine hair typically requires protein more regularly than its coarse counterpart. Protein deprivation in fine hair can often come across as a dry/unmoisturized feeling. What most girls with fine-textured curls are really feeling is protein deprivation instead of lack of moisture. Conversely, if your hair is coarse, it's, by nature, stronger than fine hair. Therefore, it doesn't need protein nearly as often as fine-haired curlies.
So, why might you think you're protein sensitive?
Now that you have a good understanding of what protein is, why it's important to have in it in your hair products and how it is or isn't absorbed, let's discuss some reasons why your own experience with protein might have been less than desirable.
Using heat on natural/curly hair is usually viewed as a bad thing. However, to best ensure that your protein treatment absorbs, bring out the hooded dryer, heat cap or steamer. This is especially important if you're low porosity! Otherwise, the protein molecules will just hang out on your hair shaft, unable to penetrate, causing a slew of undesirable or ineffective results.