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Name: Benjamin
Status: student
Age: 13
Location: N/A
Country: N/A
Date: 1999-2001

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.


Hi Benjamin!

To bleach the hair is the process of lightening its color. 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 commercial products.

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 color.

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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