What is the effect of bleaching your hair? What is the
difference between bleached hair and regular hair? Does bleach
permanently ruin your hair?
Hair bleach, like the bleach used on clothes, is an oxidizing agent. The
melanin in your hair is oxidized to a colorless compound. Along with this,
other components of your hair are also oxidized. Specifically, unbleached
hair contains thiol (-SH) groups. These help to stabilize the structure of
your hair by oxidatively cross-linking to form disulfides (-SS-). (As an
aside, perms work by breaking the disulfide bonds and then forming new ones
with the hair in the position you want it. The new disulfide bonds keep
the hair curling the way it was set.)
Thiol groups are hydrophobic (water-repellent) and slippery. Hairs with
thiol groups on them slide across each other easily. If thiol groups are
oxidized by peroxide, they go beyond the disulfide stage to the sulfonic
acid (-SO3H) stage. (Exposure to air and sun can also oxidize the thiols
to sulfonic acids.) Sulfonic acids are hydrophilic (water-attracting) and
sticky. Hairs with sulfonic acids on them tend to tangle, unless you
lubricate them. That's what conditioner is for.
Once the thiols on hair have been oxidized to sulfonic acids, there's
really no going back. The hair won't be as manageable as before, so it's
more necessary to use conditioner. New hair, of course, is still fine, so
bleach doesn't permanenetly ruin hair that hasn't grown yet.
Richard Barrans Jr., Ph.D.
Chemical Separations Group
Keep in mind that bleach is a chemical that removes color. Any harsh
can damage hair. Each person's skin and hair responds differently to
chemicals. That is why we are all unique.
To bleach the hair is the process of lightening
The different colors of hair are determined by the
quantity, type and distribution of color pigments
inside the hair. Bleaching radically alters the
original proportions of these pigments.
Regular hair is the one you have naturally
without color treatments. Bleaching can be done
with oxidants as hydrogen peroxide (H2O2) or
Bleaching does not add any color to the hair.
Coloring can be done after bleaching adding
special dyes found in commercial products.
The added color is not permanent and changes,
or fades after some time by washing or being
exposed to sunlight. Anyway the color added
(and the bleaching) does not affect the hair
inside the scalp that will grow with its natural
But be careful! Hydrogen peroxide and commercial
products either for bleaching and coloring
hair must be used properly and carefully,
following the instructions. They can hurt the
eyes and the skin. Besides the hair bleached
and colored surely will be drier and more fragile.
Thanks for asking NEWTON!
(Dr. Mabel Rodrigues)
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Update: June 2012