We believe that everyone can effortlessly grasp the importance of hydration. Water is life, simple, right?
But when it comes to water within the hair, it's not as straightforward as giving your hair a cup of water. There's more to consider than that!
The moisture levels in your hair, or the presence of water within it, play a vital role in its overall health and cosmetic appeal. Insufficient moisture over an extended period can lead to dryness, brittleness, tangles, and increased susceptibility to breakage.
This article sets out to help you understand how the hydration process triggers its influence on the hair and which factors can impede it. Also, you will learn several signs that your hair requires more hydration and how to do it properly.
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The structure of human hair and how water impacts it
The hair shaft, the part above your scalp, contains three main layers, naming the medulla, cortex, and cuticle.
(Source: In Vivo Human Hair Hydration Measurements by Using
Opto-Thermal Radiometry, Bontozoglou et al. 2019)
The Medulla Layer
The medulla, the innermost layer made of soft keratin, acts as the core of the hair shaft.
It is soft, fragile, and amorphous in appearance. This layer may even be completely absent in some cases (e.g., in naturally blonde or fine hair).
The Cortex Layer
The middle and thickest layer is the cortex, composed of spindle-shaped cortical cells.
This layer constructs the main body of the hair, and unlike the medulla, it is made of hard keratin. The cortex layer contains pigments. It gives the hair its strength and also determines the hair colour, curls pattern, thickness, and texture.
More importantly, the cortex is the predominant layer of water absorption in hair.
The Cuticle Layer
Lastly, the outermost layer of the shaft is the cuticle, consisting of scales of hardened, keratinized tissue. It is a thin, translucent coating surrounding the hair shaft.
This layer often has the imbricate pattern, which resembles the layout of tiles on a house roof, covered with a layer of lipids that helps the hair repellent to external water sources and retain moisture within the hair.
Also, the cuticle has a critical role in shaping the hair porosity - the ability to let in and retain moisture of your hair.
When the structure of the cuticle is too close together (low porosity), it hinders the penetration of hair and oils. Meanwhile, if the structure is too widely spaced (high porosity), it is harder for the hair to keep the moisture within.
That is to say, in the hair shaft, water (and other compounds) penetrate deeper through the filter of the cuticle layer, whilst the moisture level of your hair is determined by the water content existing in the cortex layer.
Did you know how to "water" your hair the right way?
On average, hair fibres contain up to 32% of water, and this figure could change significantly depending on diverse external factors, such as humidity, sun rays, temperature, or chemical treatments.
When hair is exposed to water, it swells constantly and becomes softer. Your hair can take up to 30–35% water before it gets wet entirely.
Hair hydration is the process by that water is applied and penetrates the cortex and medulla layers of the hair shaft. Moreover, the cuticle layer, thanks to its lipid film, will help lock the water within the inner layers, preventing moisture loss.
As a result, your hair gets more hydrated!
Once the hair is deprived of water or suffers from moisture deficiency, hair elasticity (or brittleness) is altered. It will become more fragile and vulnerable to damage. Even worse, dehydrated hair is prone to absorbing moisture from the surrounding environment and becomes frizzy.
That is to say, besides the ability to absorb water, how the hair seals such moisture is also significant in maintaining an optimised hydration level for your hair.
In short, hair hydration should include hydrating the hair and locking the moisture within. Otherwise, your effort could go to waste as the water content in the hair shaft remains unchanged, and your hair still stays thirsty.
What makes your hair dehydrated?
Firstly, the water content of hair depends on relative humidity (RH) to a great extent.
One study found that the hair volume increased by 12.2%, 16.3%, and 24.6% when the RH reached 40%, 60%, and 90%, respectively.
Also, the hair weight could increase up to 22.6% when HR is 86%.
One other significant inhibitor to the hydration level of hair is chemical treatment.
Reactive cosmetic hair treatments often impair fibre structure, causing adverse effects on water absorption.
For example, hair bleaching often relies on an oxidizing agent whereby melanin and other components are oxidized. Thus, the treatment can readily transform the fibre surface.
Dyeing, perming, or employing harsh products can all influence hair porosity over time. Research shows that after straightening, the hair could become significantly dehydrated.
When the cortex layer is affected by heat or harsh chemical treatments, the cuticle scales raise and become open instead of staying flat and pointing towards the hair tip. This alteration, in turn, leads to the struggle of your hair to keep moisture within.
Prolonged UV exposure will also make your hair more porous. Moreover, ageing is likely to impact the hydration level of your hair. Indeed, research findings suggest that hair at a younger age can hold water better while losing water much more slowly.
Identify the hydration issue with your hair
As you already know, hair is unique among individuals. Thus, the hydration needs for hair vary, depending on the hair type, environment, lifestyle, and hair care regimen. How do you know if your hair has a moisture deficiency?
You can recognise moisture deficiencies when your wet hair feels rough, hard and tangly. When you pull the hair strand, it doesn’t stretch much before breaking. Due to the low water content within the hair shaft, it tends to lose natural elasticity.
In addition, dehydrated hair looks lifeless and dull, with little to no shine. It is more prone to breakage as it is super fragile. Hair that lacks moisture also takes more time to feel thoroughly wet in washing as it needs to absorb more water to be fully hydrated.
On the contrary, moisture-balanced, healthy hair is very resilient when wet or dry. It should feel soft and supple, move well and appears lustrous, sheen or shiny.
How to properly hydrate your hair?
Hair hydration is not a one-time treatment.
It should be a continuous process with healing treatments and then maintenance. Anyhow, you need to recognise your hair condition prior to thinking about how to improve its hydrating condition.
To hydrate your hair adequately, you need a proper moisture hair care regimen.
One option is to create a routine to hydrate hair several times a week or whenever it feels dried out. However, if you realise that you have to apply hair moisturisers multiple times a day, you might be experiencing a porosity issue. Due to such an issue, your hair cannot effectively retain the moisture applied and gets dehydrated constantly.
You might also need to be mindful of which moisturising products you add to your regimen.
As water should be there in the ingredients list (well, there could not be any hydration without water!), watch out for heavy occlusive oils such as petrolatum.
Their large molecules, trapped on the surface of hair strands, coat the hair profusely and act as excellent moisture retainers. Research shows that film petrolatum could block more than 98% of the moisture from moving in or out of the hair.
That said, they also block all external moisture sources from taking effect. Because getting rid of such oil films is hard, it may take several wash cycles or strong cleansing actors to clear them up.
Eventually, these heavy films on the hair’s cuticle could obstruct all moisture from entering the hair’s fibres, resulting in chronic dryness.
On the contrary, lighter oils derived from plants and seeds create partially permeable coatings on the hair cuticle. They effectively penetrate and strengthen the hair shaft, yet they readily dissipate from the hair's outer layer, allowing room for subsequent moisturising endeavours.
Ensure that you layer hair care products effectively for hydrating success.
Don not use oils before or without moisturisers as they will deter moisture from entering the hair strand, worsening the dryness.
A light oil coating on top of a moisturiser product is a beneficial method. By doing that, water is introduced to the hair fibre first and then locked into place with oil.
Lastly, make sure you don’t overuse protein-based products such as hair repair or other leave-in treatments.
Protein-rich products (such as hair masks) are beneficial for cuticle repair by filling up broken spaces and adding structure to the hair strand.
However, cuticle repair can cause adverse effects through the overuse of products. The protein overload could bind strongly to the hair cuticle and undermine the water absorption ability of the hair shaft.
The ironic result? Your hair is left dehydrated and damaged due to your excessive effort to repair it.
The information we provide is not intended to mitigate, prevent, treat, cure or diagnose any disease or condition. If you have any concerns about your health, please consult your doctor.
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