A Brief Guide to the Biology of your Hair

When trying to make, buy or use products for healthy looking hair, learning about hair biology is a good place to start. The overall structure of your hair tells you a lot about what types of products or ingredients may work well for you, how you should be treating your hair and more. That will be the topic of discussion here. In this blog post, we’ll cover basic hair structure, different hair textures, damage and hair products, including how they interact with your hair biology. Enjoy!

Hair Structure

 

Your hair is made up of mostly keratin, a strong protein that’s very resistant to wear and tear. Keratin can also be found in nails and horns, but it has a softer feel in hair due to the way the hair is structured. At the cuticle, the overlapping scales (similar to shingles on a roof) are made up of this keratin protein. When in good shape the scales on your cuticle lie flat and stay tightly knit together, giving your hair a smooth and shiny appearance. In damaged hair, the cuticle starts to open up, becoming less tight-knit, and as a result, hair can eventually feel rough, coarse and brittle. This is why most hair products are designed to target the cuticle, although formulators try to make their products able penetrate all the way to the cortex.

 

Once your hair is damaged, like in the above picture, the best you can hope for hair care products is to temporarily fix (or mask) the problem. Considering hair isn't ‘alive’, these are products you’ll have to keep on applying for your hair to look healthy. An actual fix when your hair is so damaged would be to just cut it and treat it better the next time. But if you're not into that, there’s a hair care product for you :).


The structure of the hair is held together by two types of bonds, hydrogen, and disulfide. The disulfide bonds help to give your hair its strength and elasticity, keeping hair in shape- these bonds are the strongest naturally occurring bonds in nature. Disulfide bonds can be broken with high heat & certain chemicals. While hydrogen bonds in your hair are easily broken by applying water and can be briefly reset with heat - this allows you to temporarily change how your hair looks with heated styling tools, like a blow dryer or curling iron, after you wash your hair. Because of these bonds and the overall structure of your hair, hair is incredibly good at absorbing water and swelling. Hair in good condition can absorb over 30% of its own weight in water, going all the way up to 45% in very damaged hair - the diameter can increase up to about 20%! Styling aside, when your hair swells like this, it’s also more prone to damage.

What texture of hair do you have?


 

Every hair follicle has a sebaceous gland. Oils released by these glands help give your hair natural flexibility and protection, although these can easily be washed away with surfactants in shampoos. Restoring these natural fats is often the goal of hair products, especially conditioners. Hair also consists of a bit of water, somewhere between 8-14% on average. Like I mentioned above, hair is a good water absorber, making humid environments problematic for your hair. Hair anti-frizz products are designed to combat this effect since hair will behave differently depending on how much water is in it (i.e. become frizzy and more prone to damage). Despite the fact that different hair types can feel more oily or drier, classifying your hair based on these conditions may not make the most sense. This is because the shape and size of your hair really dictate how the water and oil will interact with your hair.

 


Classifying your hair based on the number of hairs on your head and the follicle diameter (i.e. straight or curly, fine or course) makes the most sense. For example, hair with a larger diameter (e.g. courser hair) is more prone to moisture evaporation and ultimately dry ends. Finer hair, on the other hand, has a much smaller diameter of the hair fibers resulting in a tendency to get oily and limp faster. Fun fact, people with fine hair don’t have less hair, just smaller hair fibers. In fact, they actually have more hairs than any other hair texture. In general, the average number of hairs on our heads is about 120000. Another fun fact, hair diameter changes as we age, starting thin, getting thicker as we approach our middle age, and thinning out as we get older.

Hair Growth

The hair follicles on your head are constantly cycling through these hair growth phases independently of each other. Note, by the time your hair reaches the head, the fiber is dead. As a result, despite marketing claims, you can’t actually make the hair healthier, you can only affect the look of it. Amazingly, approximately every 4 years or so, your whole head of hair has been replaced with new hair. Due to the fact that this growth cycle is unsynchronized at each of the hair follicles, you generally don’t notice this. Hair loss, thinning and issues with hair growth are from disruptions in this growth cycle. These disruptions can be caused by poor nutrition (i.e. restrictive eating), illness and genetics, usually resulting in the anagen phase being cut short and too many hairs entering the telogen phase at the same time. Despite many marketing claims on cosmetic labels, there’s really no effective products, especially in the cosmetic aisle, that actually are able to fix these problems, although there’s lots of research being done to find solutions. At the end of the day though,  when a product comes about that’s actually able to target hair growth, the product would be regulated as a drug and not a cosmetic product.

Note: Despite all the hair-loss type products in the market, if regulated by Health Canada they would be pulled off the shelves. Again, aside from these products not being effective, in North America, if a product can interact with your biology in this manner, it must be regulated as a drug, which would require significant efficacy testing, and not a cosmetic product.

Hair Biology Related to Hair Care Products

First things first, the pH of your hair is about 4.5 to 5.5 - quiet acidic. To avoid damaging your hair with your hair products, ensuring the products have been pH adjusted to be suitable for your hair is important. Thinking about the shape and size of your hair will give you a good idea of which type of products will work best for you. For example, different shampoo and conditioning products will be formulated to address different hair types. For products geared to coarser hair, they may be more conditioning agents and they may have less of a cleansing effect. In contrast, products geared to thinner hair, since this hair type has a tendency to get oily faster, will have less heavy conditioning agents.


Shampoos are used to clean away all the grime and skin scales from your scalp. Despite all the hype on the no-poo movement and some possible allergens in these products, dermatological studies typically agree that shampooing relatively regularly (with good shampoos) can help prevent scalp problems, such as dandruff (aside from certain yeasts, dandruff is actually related to an oily scalp rather than a dry one). With that said, the average 4-5 times a week for most North Americans (about double compared to many European countries) may be a wee bit too high. Certain ingredients in common shampoos are a little harsh on the cuticle, for example, anionic surfactants that act as cleansers. Overwashing like this, especially when these ingredients are in the products, can do a bit of damage to the cuticle. There seems to be a happy balance for how often you use shampoo - every 2-3 days may be a good amount to shoot for, but at the end of the day, wash as often as feels good for your hair.

Although shampoos are generally safe and leave your hair feeling more manageable, they also contain ingredients that are factors in emerging skin allergies that may be worthwhile to keep an eye out for. Some of these ingredients include Cocamidopropyl betaine, formaldehyde-releasing preservatives, propylene glycol, certain parabens, and benzophenones.

With respect to the no-poo (no shampoo) movement, most of the claims made regarding shampooing less for more balanced hair are completely anecdotal. In addition, something that’s quite common in this movement is washing your hair with baking soda. Remember how I said your hair is quite acidic? Well, baking soda is very alkaline with a pH at about 9. Washing with this ingredient will almost certainly damage your hair, most likely leaving your hair feeling more like straw.

Conditioners on the other hand help to detangle hair, reduce frizz, seal the cuticle, and enhance the shininess and smoothness of your hair. Conditioners are made up of a variety of moisturizing and conditioning ingredients that are left behind after you rinse - this is key in conditioners. These ingredients include different surfactants (quaternized), silicones, humectants, emollients, proteins, B vitamins (especially panthenol/B5), etc. While silicone can definitely help to make your hair nice and smooth, if it’s too high in the ingredient list of a product (i.e. top three ingredients), it can cause brittleness and dullness. Dimethicone is the most widely used silicone in the hair care industry. Finally, to get the best bang out of your shampoo and conditioners, when you shampoo, use it mostly on the roots of your hair and scalp. When you condition, especially if you have thinner hair, apply it mid-shaft to tips, avoiding your scalp.This will save you money, keep your hair healthier looking and make it easier not to shower every single day.

Note, while certain organizations deem silicones as bioaccumulative to the environment and potentially bad for us (i.e. an endocrine disruptor), there’s actually not a whole lot of evidence to support these claims. In addition, there are many different types of silicones used in the cosmetic industry. At the end of the day though, more research should be done to further evaluate these ingredients. If your formulating products, blends of waxes and botanical oils can offer a nice and natural silicone replacement.

There’s so much more to learn about hair biology and hair care products but I think this is a good start! If you have any questions, queries, conundrums or concerns, leave them below in the comments, on The Eco Well's Facebook page or shoot us an email!


References:

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  5. Nazir H, et al. (2011) Uniform-sized silicone oil microemulsions: Preparation, investigation of stability and deposition on hair surface. J Colloid Interface Sci.364:56–64.
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