Environment,
weathering and hair color changes
While the primary causes of hair color are due to our genes and
their effects on the amount and type of melanin pigment production,
there can also be changes in hair color due to environmental influences.
The environment can affect hair in two ways, by physical action
and by chemical reaction.
Chemical action on the hair is arguably becoming more of a problem
with the increased frequency of chemical exposure that individuals
encounter with modern living. Melanin pigment can be altered through
interaction with acids and alkalis. Acid interaction darkens hair
while alkali lightens hair color. Whether acid and alkali in air
are present in high enough quantities to significantly interact
with hair pigment remains to be determined, but acids and alkali
are encountered in water supplies and as detergents in shampoos.
Such exposure to acid and alkali solutions can affect hair color.
The effect of sunlight on hair can have a direct effect on color
that may be accentuated in the presence of polluted air. With time,
UV light degrades melanin pigment and bleaches the hair fiber. Black
and dark brown hair may change into a lighter brown. Light brown
and blonde hair can be bleached completely white with chronic sunlight
exposure.
Hair color may seem to change as a result of physical actions on
the hair or "weathering". A healthy hair cuticle is fairly
smooth and this gives hair a richer color. However, a poor cuticle
is rough and flaky or sometimes the cuticle may be completely stripped
away. This rough surface to the hair fiber results in much reflection
and refraction of light. This gives an observer the impression that
the hair color is lighter than it actually is. The color also has
a dull dry appearance. Such physical weathering and consequent hair
color changes most commonly occurs in people with heavily processed
hair, those who use harsh detergents for washing, and those who
excessively brush or otherwise manipulate their hair. In people
with long hair the observer may see a color change from root to
tip. The ends of the hair are the oldest hair and thus will be the
most weathered hair. The hair roots are new hair and the cuticle
here should be least damaged. As a result, the hair ends may seem
to have a lighter color than the hair roots.
Bathing in salt water, whether it is sea water or high mineral
salt containing tap water, can affect hair color. Whilst the salts
dissolved in water might chemically interact with the pigment in
hair, they may also affect the physical properties of the hair fiber.
As hair washed in salt rich water dries out the salts may crystallize
within the hair fiber and cuticle. This may physically break down
the structural integrity of the hair and lift up the cuticle. The
result may be weathered hair and an apparent reduction in hair color.
Some people are more susceptible to environment induced hair color
changes than others as a result of secondary internal factors such
as hormones and general genetic disposition. So while some people
can wash their hair with strong alkali detergents with impunity,
others with exactly the same hair color may find the same treatment
significantly affects their hair color.
Environment,
weathering and hair color changes references
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Jul;122(7):750-2.
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Nov;107(5):517-27.
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in human hair. Br J Dermatol. 1976 Jul;95(1):111-2.
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