The science behind healthy hair

What is healthy hair and what is the science behind it? Here we discuss the structure of the hair and its propensity to exhibit a healthy appearance or not. Why can our locks look lackluster?

Healthy hair. Image credit: Prostock-studio /

A better understanding of the natural properties of our hair has led us to use conditioning treatments to manage and improve its appearance. In recent years we have seen a growing demand for natural and sustainable hair care products. Here we take a closer look at the use of plants in hair care.

What does healthy hair look like?

Healthy looking hair is generally considered to be smooth and shiny as opposed to dull, coarse and frizzy. The virtues of smoothness and shine relate to the properties of the hair surface. The clean cut or tapered ends are additional indicators of health and refer to the cortex of the hair.

Among the reasons a person might be left struggling with an unhealthy-looking set of locks include excess styling and cosmetic treatments, such as the use of chemical dyes or bleach. Chemical damage can occur here to contribute to a dull, frizzy and dull appearance of the hair. Additionally, age-related changes such as natural graying or androgenetic alopecia (hair loss in older men) can cause loss of luster and smoothness.

To keep our hair healthy it is necessary to coordinate a complex set of elements; an interplay between medical and biological factors, scalp care habits, hair care procedures and environmental factors. Cosmetics are used to alter the physical and mechanical properties of hair, which in turn depend on the internal structure and protein constitution. The surface of the hair, when viewed as “structured” at the molecular level, has implications for the design of eco-friendly and sustainable ingredients and formulations for both shampoos and conditioners and these products have seen an increase in consumer demand in recent years.

How is the structure of the hair?

The hair structure consists of an outermost hydrophobic layer together with a cortex. Taken together, these layers impart the coveted physical properties of shine (luster) and volume (body) necessary for the designation of hair “health”.

The hydrophobic lipid epicutic layer comprises flattened overlapping cuticle cells. The normal cuticle has a smooth appearance and allows for light reflection. Meanwhile, the inner cortex is made up of tightly packed spindle-shaped cells filled with keratin filaments. Permanent changes occur in the cortex when the hair is exposed to treatments such as coloring or procedures such as curling or straightening.

Shampoo and conditioner go hand in hand

The shampoo acts as a cleanser to remove excess oil, sebum and dirt. However, when used alone, it leaves wet hair tangled, difficult to manage and prone to fizz after drying. Poor combing technique can cause mechanical stress and lead to the removal of the covalently bonded outermost lipid layer, leaving the hair surface hydrophilic and ionized.

One solution to this problem is the application of conditioning treatments to the hair after shampooing or the combination of shampoo and conditioner in a single application: a maneuver that saves time. The challenge in both cases (shampoo + conditioner or a formulation where the two are combined) is to keep the conditioning ingredients on the surface of the hair after the cleansing formulation has been removed. The most common conditioning ingredients are made up of cationic surfactants, cationic polyelectrolytes, lipophilic conditioners (such as oils, natural waxes, fatty alcohols) and silicones.


The shampoo acts as a cleanser to remove excess oil, sebum and dirt. Image Credit: Mr. Cheangchai Noojuntuk /

The demand for natural and sustainable products

The cosmetic industry has tried to meet the demands for more natural and sustainable products. The big challenge here is being able to replace traditional low-cost surfactants with new biosurfactants and for a similar price. Great strides have been made in this direction using the principles of green science and many new ingredients are now environmentally friendly.

In the search for more natural solutions, there has been the recent development of solid shampoos that pack in new and interesting ingredients. They are mainly based on clays, herbs or flours, as an alternative to traditional washing bases, combined with the usual synthetic surfactants and other common ingredients.

There are several advantages of solid shampoos over traditional formulations, such as ease of transport and better microbiological stability (the presence of water in the composition of traditional shampoos requires the use of additional preservatives). Below we will focus on the use of herbs.

The use of herbal hair cleansing products has been known since time immemorial. In recent times there has been a resurgence in the use of herbal medicine in conjunction with the growing trend in favor of natural raw materials. Herbal products are also preferred because they offer the added benefits of being low cost, as well as offering a low risk of side effects.

A whole plethora of plants has been found to be beneficial for our hair. The benefits are conferred through such sought-after components as vitamins, amino acids, sugars, glycosides, bioflavonoids, phytohormones, fruit acids and essential oils. The challenge lies in the selection of these natural ingredients, together with the advent of new formulation techniques.

Although these new formulations include natural components from which we could connote a sense of protection, it remains essential that they are, in fact, safe and efficient for long-term use. Many herbal shampoos available still rely on synthetic ingredients, although the formulation of “pure” shampoos using only natural ingredients is now known to compete with traditional shampoos in their much desired characteristics of lather, mild detergent and solid content.


  • Gubitosa, J. et al. 2019. Hair Care Cosmetics: From Traditional Shampoo to Solid Clay and Herbal Shampoo, a review. Cosmetics. Doi: 10.3390 / cosmetics6010013.
  • Luengo, G. et al. 2020. Surface science of cosmetic substrates, active detergents and formulations. Advances in colloidal and interface science. Doi: 10.1016 / j.cis.2021.102383.
  • Sinclair, R. 2007. Healthy hair: what is it? Proceedings of the symposium of the Journal of Investigative Dermatology. Doi: 10.1038 / sj.jidsymp.5650046.

Further reading

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