How To Keep Your Hair Moisturised All Year Round

WrittenbyLuat Duong
Last updated

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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 Properly moisturizing your hair is crucial to prevent common issues like dryness, brittleness, tangles, and breakage. It's not as simple as just giving your hair a cup of water.

The relative humidity in your surroundings significantly impacts the moisture level of your hair. It can swell when exposed to water, but its ability to retain this moisture depends on the hair's porosity.

Hair treatments, such as bleaching or perming, can affect the hair's ability to absorb and retain water. These treatments alter the hair's structure, making it more porous and, as a result, more prone to dehydration.

To maintain well-hydrated hair, choose products that contain water and avoid heavy occlusive oils like petrolatum.  It's also important to avoid excessive use of protein-based treatments, as they can disrupt the hair's moisture balance and lead to dryness.


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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.

The structure of hair shaft

(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. 

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Hair Hydration Mask
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Hair Protection Oil
Hair Protection Oil
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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. 

Relative humidity affects greatly the hair moisture levels


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.


Does your hair need more moisture?


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.


Products layering is key to effective hair hydration

(Source: The science of black hair, Davis-Sivasothy 2011)


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.



Barba, C., Martí, M., Manich, A. M., Carilla, J., Parra, J. L., & Coderch, L. (2010). Water absorption/desorption of human hair and nails. Thermochimica Acta503, 33-39.

Benzarti, M., Pailler-Mattei, C., Jamart, J., & Zahouani, H. (2014). The effect of hydration on the mechanical behavior of hair. Experimental Mechanics54(8), 1411-1419.

Breuer, M. M. (1972). The binding of small molecules to hair I: The hydration of hair and the effect of water on the mechanical properties of hair. J. Soc. Cosmet. Chem.23, 447-470.

Bontozoglou, C., Zhang, X., Patel, A., Lane, M. E., & Xiao, P. (2019). In Vivo Human Hair Hydration Measurements by Using Opto-Thermal Radiometry. International Journal of Thermophysics40(2), 1-11.

Egawa, Hagihara, M., & Yanai, M. (2013). Near-infrared imaging of water in human hair. Skin Research and Technology19(1), 35–41.

Murthy, Wang, W., & Kamath, Y. (2019). Structure of intermediate filament assembly in hair deduced from hydration studies using small-angle neutron scattering. Journal of Structural Biology, 206(3), 295–304.

Yu, Y., Yang, W., Wang, B., & Meyers, M. A. (2017). Structure and mechanical behavior of human hair. Materials Science and Engineering: C73, 152-163.

Davis-Sivasothy, A. (2011). The science of black hair: A comprehensive guide to textured hair care.

Luat Duong

Luat Duong is a Copenhagen-based writer and content strategist specializing in hair loss and health. His work has been featured in MyHealthGuide, The Right Hairstyles, and Woman's Era. He is a graduate of Vaasa University. You can connect with him on LinkedIn.