442 JOURNAL OF COSMETIC SCIENCE
THE COUNTER ARGUMENT
As highlighted above, it is possible to rationalize all manner of differences in hair properties,
that might traditionally be associated with being from different “hair types” without the
need for a difference in makeup. However, upon digging deeper, some curiosities emerge.
Most obviously, it is well recognized that chemical treatments can give rise to very
different outcomes when applied to hair from different heads. For example, application of
a permanent wave to one head might produce the exact desired outcome but might also be
wholly ineffectual when applied in exactly the same manner to the next head a bleaching
treatment might give rise to substantial lightening on one head, but considerably less on
the next.
While the activity of daily-use hair-care products (e.g., shampoos, conditioners, and styling
products) relates to the hair surface, so-called chemical treatments involve ingredients that
penetrate the inner cortex and engage in chemical reactions. In the case of perms, it has
been shown that progression rates can vary considerably when testing hair procured from
different individuals.9 Two explanations may be hypothesized: either chemical reaction rates
vary, or ingredient permeation rates differ. Given that this occurrence arises in treatments
that involve very different chemistries, attention would seem to fixate on the second option.
In support, penetration rates are facilitated at an elevated pH and can also be seen when
testing damaged hair where, in both cases, hair fibers can swell to greater extents. So,
a theory arises that hair from different heads can potentially swell to different degrees,
which subsequently dictates the progression rate of the desired transformation. This author
has generated some data that would seem to agree with the above hypothesis but not yet
enough for confirmation. However, returning to the point at hand, differing degrees of
swelling seemingly suggests different internal structures.
Figure 16. Statistical distributions for fiber diameters in Caucasian and Asian hair.

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