443 SUSTAINABLE HAIR
Further to this point, single fiber fatigue testing on hair samples procured from a high
number of panelists has suggested sizable differences in measured properties. On the one
hand, very different breakage properties are seen among individuals, but also notable
differences in the measured Young’s modulus are obtained.44 As discussed earlier, the
mechanical properties of hair are attributed to the internal cortex structure so, a difference
in the measured modulus implies different structural makeup.
Reaching conclusions in all the previous studies is complicated by the potential for an
overriding effect of hair damage. As already highlighted, various insults can impact swelling
rates, mechanical properties, and a propensity for breakage so, when testing panelists’ hair,
it is never certain whether the natural innate properties are being evaluated or the state
that exists after any degree of various insults. In the case of the mentioned breakage study,
a degree of confidence is attained as the result of the very high number of panelists tested
(over 100). Clear trends were found while scatter and outliers were likely consequences of
hair that had experienced progressively higher degrees of damage.
The concept of differing internal structure is not unheard of in the hair world. Studies
on wool in the 1950s led to the postulation of different types of cortical cells and their
subsequent arrangement within fibers.45,46 Specifically, especially kinky Marino wool was
found to have a bilateral symmetry involving so-called ortho and para cortical cells. This
same conformation has subsequently been observed in very curly African hair,47 while
an annular arrangement appears to be present in straight hair.48 Further, the existence of
additional cell types has also been proposed.49,50
As highlighted, these considerations have no relevance to the activity of conventional daily-
use products, which are overwhelmingly the dominant players in the hair-care market.
Therefore, despite being an intriguing curiosity, there does not appear to be industry
drive for further study of what seems to be a major question involving hair’s fundamental
structure.
CONCLUSION
After creating such a wonderous material, Mother Nature could never have conceived of all
the toils that would be inflicted on hair in the name of beauty. For the most part, consumers
appear generally aware of the harmful effects of various harsh habits and practices yet, the
end outcomes often outweigh and justify the means. At the same time, consumers have
inexplicably and erroneously decided that passive ingredients (such as sulfated surfactants,
silicones, etc.) are villains to be avoided at all costs. The gaps between consumer beliefs
and the fundamental underlying science have steadily widened since the advent of social
media, blogging, and influencers. Perhaps the sometimes-seen proposition of a product/
formulation being “chemical free” is the most egregious example. When this author joined
the industry over 30 years ago, it was mostly self-police, with big companies challenging
each other if it was felt that propositions and claims were excessive and/or misleading.
In today’s world of e-commerce, which has led to a proliferation of small players, this
has become an almost impossible task. Ironically, it now feels that our industry is being
patrolled by lawyers who seek class action lawsuits against those believed to be deceiving
consumers (often in a manner that feels like cosmetic ambulance chasing).
The moment hair egresses out onto the scalp, it begins to be exposed to a myriad of
potential insults. Some of these are relatively mild, while others are considerably more

444 JOURNAL OF COSMETIC SCIENCE
severe. Moreover, this continues over the lifespan of the fibers, which is generally around
three to six years. Hair grows at a rate of approximately 0.5 in per month, and the tips of
shoulder-length hair have accumulated the sum of two years’ worth of such insults. Not
surprisingly, despite its tough, strong makeup, the hair structure progressively degrades
with commensurate alteration in its physical properties. Most often these changes are
detrimental to the wearer. Tactile properties worsen, the hair becomes more unruly, and a
higher propensity for breakage may be encountered. This article has attempted to describe
the underlying technical reasons for these occurrences although, as explained, our industry
fixates on consumer language which causes considerable confusion. For example, as shown,
despite consumer beliefs, hair does not physically “dry out” and therefore does not need to
be “moisturized.” Indeed, the science shows that hair has decidedly poorer properties when
its water content is raised.
Hair-care products play an important role in the well-being and maintenance of hair.
Shampoos remove sebum, exogenous soils, and product residues that would otherwise
build up and leave hair feeling greasy, dull, and weighed down. Conditioners coat the hair
with a thin, aesthetically pleasing lubricating layer that improves feel, aids with grooming,
helps reduce abrasion, and can lessen fiber breakage. While these are all highly desirable
benefits (which most consumers likely could not do without), in the marketing world there
is always the need for a new story. Accordingly, messages become increasingly grander:
attractive sounding but nonfunctional ingredients are touted, false promises are made,
the fundamental science takes a backseat, and the credibility of our industry suffers. It is
hoped that this article helps to emphasize and reinforce the differences between science and
marketing as well as the differences between scientific language and consumer language.
REFERENCES
(1) ReferencesFortune business insights. Hair Care Market Size, Share &Industry Analysis 2024, August 5.
https://www.fortunebusinessinsights.com/hair-care-market-102555.
(2) Evans TA. How damaged is your hair? – Part 1: Surface damage. Cosmet Toiletries. April 2017 132(4):38–48.
(3) Evans TA. How damaged is your hair? – Part 2: Internal damage. Cosmet Toiletries. June 2017 132(6):36–45.
(4) Evans TA. How damaged is your hair? – Part 3: Better defining the problem. Cosmet Toiletries. July/
August 2017 132(7):58–67.
(5) Robbins CR, Chapter 1. Morphological and macromolecular structure. In: Chemical and Physical Behaviors
of Human Hair. 5th ed. Springer-Verlag.
(6) Swift JA. The structure and chemistry of human hair. In: Practical Modern Hair Science, T. Evans and R.R.
Wickett. Allured Publishing 2012.
(7) Franbourg A, Leroy F. Hair structure, function and physiochemical properties. In: The Science of Hair
Care, C. Bouillon and J. Wilkinson. CRC Press 2005.
(8) Marshall RC, Orwin DFG, Gillespie JM. Structure and biochemistry of mammalian hard keratin.
Electron Microsc Rev. 1991 4(1):47–83. doi:10.1016/0892-0354(91)90016-6
(9) Evans TA. A Review of permanent waving and perm chemistry. J Cosmet Sci. 2021 72(1):99–133.
(10) Robbins CR, Kelly CK. Amino acid analysis of cosmetically altered hair. J Cosmet Sci. 1969 20:555–564.
(11) Hoting E, Zimmermann M, Hilterhaus-Bong S, Schwarzkopf H. Photochemical alterations in human
hair. I. Artificial irradiation and investigations of hair proteins. J Soc Cosmet Chem. 1995 46(2):85–99.
(12) White HJ, Stam PB. An experimental and theoretical study of the adsorption and swelling isotherms of
human hair in water vapor. Tex. Res. J. 1949 19:136–151.