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Does Hair Contain Water?

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Table of Contents

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Hair is a fascinating, complex structure primarily composed of alpha-keratin protein. This protein forms the backbone of hair through its polypeptide strands, which are intricately linked by various chemical bonds.1 Just like other biological materials, water plays a pivotal role, and keratin is no exception. Keratin has a remarkable ability to adsorb and retain water molecules.2

To answer the question, “Does hair contain water?” – yes, it certainly does. Hair fibers house water in two forms: external, where water molecules are adsorbed onto the surface, and internal, where water is inherently present within the hair’s structure. The interaction between water and the hair’s keratin significantly affects the hair’s appearance, texture, and manageability. Moisture levels within the hair can drastically influence its health and ease of styling, underlining the popularity of products labeled as “Hydrating” and “Moisturizing” in the beauty industry.

Understanding the scientific nuances behind water’s role in hair health sheds light on why maintaining optimal moisture levels is crucial. Water’s bonding with keratin’s amino acid sites is essential for hair’s elasticity, strength, and overall appearance. Insufficient moisture leads to dry, brittle strands that are challenging to manage and style, highlighting the importance of a proper hair care regimen that supports hydration.

For an expert perspective on this topic, I’ve consulted with a friend, a seasoned hair scientist and cosmetic formulator with a PhD in Chemistry. His expertise offers invaluable insights into the intricate relationship between water and hair, providing a deeper understanding of achieving and maintaining healthy, vibrant hair through proper moisture management.

Hair Hydration Dynamics: Moisture Content and Environmental Effects

Hair, much like other proteins, possesses the inherent ability to adsorb water molecules. This capacity to adsorb water is influenced by various factors, including the specific characteristics of the protein, the structure of bonded amino acid bonds, and the relative humidity levels of the environment, Consequently, hair does contain some level of water molecules, which plays a crucial role in its health and appearance.

How Much Water Does Hair Contain?

The quantity of water present in hair can fluctuate significantly based on the condition of the hair fiber and the relative humidity of the surrounding air. Scientific studies indicates that as the humidity increases, so does the moisture content of hair.

For instance, at a standard humidity level of 65%, hair’s water content can range from 14 to 16% of its total weight. This percentage escalates with rising humidity levels, reaching a saturation point at 100% humidity, where hair might absorb water amounting to 30 to 33% of its dry mass.2,3

Understanding these dynamics is essential for managing hair’s health effectively, as it underscores the importance of adapting hair care practices to accommodate varying environmental conditions.

How Important is Water in Hair Health?

Water is essential to life and plays a pivotal role in maintaining the health and vitality of hair. Acting as a universal solvent, it facilitates the transportation of nutrients, minerals, and bioactive compounds through the layers of protein that make up hair. This process is vital for nourishing the hair from within, ensuring it remains hydrated, lustrous, and resilient.

In the science of hair care, moisture is more than just a benefit—it’s a necessity. Hair lacking in moisture becomes rough to the touch and loses its natural shine and texture. Such dry strands are not only difficult to manage and style but are also prone to losing their essential lipids. This loss increases the hair’s porosity, particularly affecting the outermost cuticle layer, which can lead to increased susceptibility to damage and breakage.

Therefore, maintaining adequate moisture levels in hair fibers is not merely about aesthetic appeal; it’s about preserving the structural integrity and health of the hair.

Understanding Hair and Water Interactions

Hair fibers, primarily composed of keratin, exhibit a porous nature characterized by countless tiny pores across their surface. These pores serve as gateways for water molecules to penetrate the hair, moving beyond the outer cuticle layer and potentially reaching the inner cortex.

The process of water adsorption and penetration into the hair fiber is driven by a gradient potential, facilitating a two-way passage mechanism of moisture movement. Essentially, the presence of water molecules outside the hair shaft increases the likelihood of their absorption and deeper penetration into the hair. Conversely, in dry conditions, these water molecules can evaporate or be released from the hair fiber.4,5

The structure of hair is layered, with the cuticle acting as the external barrier and the primary point of contact for water molecules. Initially, water is adsorbed by the cuticle layer, which, thanks to its porous nature, allows these molecules to traverse deeper into the cortex. It’s important to note, however, that the bonding mechanisms and the distribution of water molecules vary significantly between the cuticle and the cortex layers.

Infographic showing the increase in hair's diameter with increasing humidity level.

The Molecular Bonding of Water and Keratin Amino Acids

Understanding the interaction between water molecules and the amino acids in keratin sheds light on the fundamental processes that maintain hair’s moisture. Keratin, the protein that constitutes hair fibers, is composed of both acidic and basic amino acids. These amino acids are interconnected through salt linkages—electrostatic chemical bonds formed between positively and negatively charged sites. Water molecules, due to their polar nature, are attracted to these charged sites and form hydrogen bonds with them.

This crucial interaction begins with the disruption of the existing salt linkages, making way for the establishment of hydrogen bonds between the water molecules and amino acids. As a result, multiple water molecules can link together, creating a chain-like structure through hydrogen bonding. This sequence of events leads to the formation of a water molecule matrix within the hair fiber layers, essentially embedding moisture into the hair’s structure.

Key Factors That Affect Hair’s Water Absorption

This section outlines the primary elements that determine the ability of hair fibers to absorb and retain water.

The Ethnic Origin of Virgin Hair

Water absorption by hair is influenced by a variety of factors, with the ethnic origin of virgin hair playing a significant role. Hair fibers exhibit a wide range of characteristics based on ethnic backgrounds, including variations in texture, curl patterns, coarseness, surface friction, porosity, and natural moisture levels.

For instance, Afro-textured hair is often characterized by its extreme dryness, attributed to lower water and lipid content compared to other hair types. This inherent dryness contributes to its fragility, making Afro-textured hair more susceptible to breakage under force.6

The diversity in hair properties underscores the importance of understanding and addressing the unique hydration needs of different hair types to maintain their health and integrity.

Humidity Level

Humidity plays a pivotal role in the process of water absorption in hair fibers, as demonstrated by experimental research. The relationship between the relative humidity of the air and hair’s capacity to adsorb water is direct; as humidity increases, so does the rate at which hair absorbs moisture. This absorption occurs under the influence of osmotic pressure, with high humidity conditions leading to air being heavily saturated with water molecules.

In environments of high humidity, water molecules are more inclined to adhere to and penetrate the keratin fibers of the hair. Conversely, in settings with low humidity, the air contains fewer water molecules compared to those inside the hair fiber, resulting in the evaporation of water from the hair. This loss of moisture can leave the hair dry and brittle.7,8

Consequently, the external humidity level significantly impacts how effectively hair fibers can absorb and retain moisture, underlining the importance of considering humidity in hair care routines.

Porosity Level

Hair porosity, which refers to the density and size of the pores on the hair shaft, is a critical factor in determining a hair’s ability to absorb water. Hair with high porosity has a greater number and larger pores, often a consequence of damage and protein loss from harsh chemical treatments. Such hair tends to absorb water more readily, leading to significant swelling of the fibers. This absorption and swelling can result in noticeable frizz, particularly in chemically treated hair when exposed to wet and humid conditions.

Conversely, hair fibers characterized by low porosity—typically virgin hair that hasn’t been subjected to chemical treatments—demonstrate a lesser degree of water uptake. As a result, these hair types are less prone to frizz under similar humidity conditions, maintaining a smoother appearance.

Understanding the level of hair porosity can thus inform more effective hair care strategies, particularly in managing hydration and styling.

The pH Level of the Cosmetic Products

The pH level of cosmetic products plays a significant role in how effectively hair can adsorb water. Scientific findings indicate that hair tends to absorb more water when exposed to alkaline conditions, whereas acidic environments lead to minimal water adsorption. In alkaline media, the hair shaft expands and the pores open, which not only facilitates the entry of water molecules but also allows for the deeper penetration of other active ingredients.

Moreover, alkaline pH conditions lead to the dissociation of amino acids in the keratin protein, resulting in an increase in negatively charged sites on the hair. These sites attract the polar ends of water molecules, encouraging the formation of hydrogen bonds.

On the other hand, in acidic conditions, amino acids are fully protonated, making them unavailable for hydrogen bonding.2 This distinction underscores the importance of considering the pH of hair care products in relation to hair’s hydration needs and overall health.

Strategies for Maintaining Optimal Hair Moisture Levels

Maintaining the correct water level within hair fibers is crucial for ensuring hair’s health, manageability, and ease of styling. A well-hydrated hair not only looks healthier but is also easier to manage. Here are some recommended steps to achieve and maintain evenly hydrated hair fibers, forming the basis of an effective hair care routine:

  1. Preventive Measures: The first step towards maintaining hair moisture is to prevent damage. Limit exposure to harsh chemical treatments and UV radiation, which can increase the hair’s porosity, making it more susceptible to excessive water uptake and subsequently, moisture loss.
  2. Minimize Heat Damage: Thermal treatments, such as blow-drying or using heated styling tools, can significantly accelerate moisture loss from the hair shaft. Experimental evidence shows that higher temperatures correlate with increased water loss, often visible under a microscope as tiny bubbles indicating steam and cuticle rupture. It’s advisable to minimize heat exposure by using styling tools at lower temperatures and always applying a heat protectant product beforehand.
  3. Customized Hydration Therapy: Establishing a personalized hydration regimen is essential. This should include gentle cleansing, application of a hydrating conditioner, and use of leave-in conditioners. For those with particularly dry, damaged, or chemically treated hair, incorporating an intensive deep conditioning and hydrating mask treatment can be especially beneficial in restoring hair’s natural moisture balance.
  4. Selecting the Right Products: Opt for deep hydrating masks that feature a combination of humectants, emollients, cationic fiber softening agents, and proteins. The effectiveness of a hair care product is not dependent on a single ingredient but rather on how these components work together synergistically to hydrate and condition the hair effectively.

Maintaining Healthy Hair: The Importance of Optimal Moisture Levels

Hair inherently contains water, which is crucial for its health and appearance. The keratin protein within hair fibers has the ability to absorb water, leading to swelling and an increase in weight proportional to the moisture content. The efficiency and degree of this water absorption are influenced by various factors, among which the relative humidity of the environment plays a significant role. Additionally, the porosity of hair—a reflection of the size and abundance of pores in the hair shaft—directly impacts its capacity to absorb moisture, with higher porosity facilitating greater water uptake.

For hair to remain healthy and vibrant, it’s vital to maintain a balanced level of moisture. Both excessive and insufficient moisture levels can detrimentally affect hair’s quality, texture, and its aesthetic attributes. Implementing a tailored hair care routine that incorporates hydrating products is key to ensuring hair remains uniformly hydrated. Such a regimen not only supports the intrinsic health of the hair but also enhances ease of styling and daily management, contributing to the overall well-being and appearance of hair.


  1. Popescu, C.; Höcker, H., Hair—the most sophisticated biological composite materialChemical Society Reviews 2007,36 (8), 1282-1291. ↩︎
  2. Zviak, C., The Science of Hair Care. Taylor & Francis: 1986. ↩︎
  3. Barba, C.; Martí, M.; Manich, A.; Carilla, J.; Parra, J.; Coderch, L., Water absorption/desorption of human hair and nailsThermochimica Acta 2010, 503, 33-39. ↩︎
  4. White Jr, H. J.; Stam, P. B., An experimental and theoretical study of the adsorption and swelling isotherms of human hair in water vaporTextile Research Journal 1949, 19 (3), 136-151. ↩︎
  5. Breakspear, S.; Frueh, P.; Neu, A.; Noecker, B.; Popescu, C.; Uellner, Q., Learning from hair moisture sorption and hysteresisInternational Journal of Cosmetic Science 2022, 44 (5), 555-568. ↩︎
  6. Franbourg, A.; Hallegot, P.; Baltenneck, F.; Toutaina, C.; Leroy, F., Current research on ethnic hairJournal of the American Academy of Dermatology 2003, 48 (6), S115-S119. ↩︎
  7. Robbins, C. R., Chemical and Physical Behavior of Human Hair. Springer Berlin Heidelberg: 2012. ↩︎
  8. Marsh, J. M.; Gray, J.; Tosti, A. Healthy hair; Springer: 2015. ↩︎


I’m just a girl who transformed her severely damaged hair into healthy hair. I adore the simplicity of a simple hair care routine, the richness of diverse textures, and the joy of sharing my journey from the comfort of my space.

My mission? To empower others with the tools to restore, and maintain healthy hair, and celebrate the hair they were born with!

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