Are Hair Bleaching and Dying Ingredients Safe?

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We may not all want to admit it, but many of us dye our hair to get the color currently on our heads. Whether we’re covering grays or trying to get a color we think is more “interesting,” we change out strands to all sorts of colors.

But how safe are these ingredients that we religiously put in our hair every four to six weeks? Well, they can certainly be damaging to hair and definitely are capable of causing skin irritation. But as for more concerning issues, such as whether they cause cancer, the studies disagree.

What’s are the Main Ingredients in Hair Bleach and Hair Dye? How Do They Affect Hair?

Oftentimes, hair dying uses both bleach and dye to get the color right.
Oftentimes, hair dying uses both bleach and dye to get the color right.

The main ingredient in hair bleach is hydrogen peroxide, the main oxidizing agent, in an alkaline solution (Hair and Hair Care). The alkaline solution helps the formula to maintain a pH somewhere around nine to 11 (Chemical and Physical Behavior of Human Hair).

The main ingredient in hair dye is p-phenylenediamine, which turns brown when oxidizing agents — like air — are present. It’s also used for dying wigs and furs, as well as an agent for developing photography (American Chemical Society). Still, the industry has been working on newer, more sophisticated hair dying agents.

Hair dying often involves some hair bleaching. If you go lighter, then hydrogen peroxide is generally involved. Hydrogen peroxide works by breaking the disulfide bonds of cystyl residues in the fiber. During normal bleaching, 15-25 percent of the bonds might be broken, during more intense bleaching (frosting or taking hair from black to blond), up to 45 percent of these bonds might be broken.

Essentially, hydrogen peroxide enter the hair when it causes the cuticle to swell and breaks down the melanin (American Board of Certified Hair Colorists). In doing this, it releases some peroxide free radicals.

Unfortunately, when the pigments in your hair are degraded, your hair loses sun protection and is more likely to lose luster, softness, moisture, etc. (International Journal of Trichology). Darker colors use less hydrogen peroxide or none at all, which can help preserve your hair.

Irritation from Hair Bleach and Dye

To avoid chemical burns, make sure procedure for hair bleaching is followed. Also, patch test to make sure you don't have an allergy to hair coloring ingredients.
To avoid chemical burns, make sure procedure for hair bleaching is followed. Also, patch test to make sure you don’t have an allergy to hair coloring ingredients.

We do know that irritation can be an issue for those who use hair dyes and bleach.  It’s possible to have a severe allergy to p-phenylenediamine, which is why it’s important to patch test before using them (DermNet NZ). It can also cause dermatitis, eye irritation, and tearing, among other ailments (US EPA).

And if the proper procedure isn’t used for bleaching hair, it’s possibly to have severe chemical burns, as in these two case studies (Acta Dermato-Venereologica). Hydrogen peroxide has also been shown to cause an increase in sensitization to contact dermatitis for hair stylists who come into contact with it frequently (Dermatitis). And patch tests in these two case studies demonstrate how hydrogen peroxide can cause contact dermatitis with short-term contact (Contact Dermatitis).

Does Hair Bleach and Dye Cause Cancer? 

As of right now, no studies have linked hair dye or bleach with a significant increase in cancer, though there are some studies that show slight increases for certain kinds of cancers (American Cancer Society).

So far, there has been at least one quality study that has linked non-Hodgekins Lymphoma, multiple myeloma, acute leukemia, and bladder cancer with exposure to hair dye and bleach, but these results were not consistent throughout all the studies (Journal of Toxicology and Environmental Health). The studies looked primarily at people — barbers and hair stylists — who face the risks associated with occupational exposure. And because there is disagreement amongst studies, researchers are calling for further testing.

However, some of the ingredients in dyes used before 1980 — like aromatic amines — were associated with cancer in animals in laboratory studies (National Cancer Institute, Critical Reviews in Toxicology). Studies point out that women and men exposed to pre-1980 formulations have a higher risk of cancer than those using current formulations. These ingredients have been removed, but it is not known whether other ingredients in hair dye might be carcinogenic.

Bottom Line

Hydrogen peroxide and p-phenylenediamine are the ingredients primarily used in hair bleach and hair dye. While p-phenylenediamine changes to brown colors when it oxidizes, hydrogen peroxide bleaches hair by breaking down melanin when it oxidizes. For this reason, lighter dyes, which take away some of hair’s natural protection, tend to make hair dryer.

There is some concern amongst people that hair dye ingredients may cause cancer, but there isn’t enough research to back this. Studies conflict over whether certain kinds of cancers are more common amongst regular hair dye users.

We do know, however, that hair dye and bleach can cause irritation of the skin, eyes, nose, and throat. It’s possible to have an allergic reaction or a case of contact dermatitis. Just be sure to patch test before dying your hair.

If you want to eschew hair dye, your options for lightening are limited, as anything that bleaches your hair will break down some of its protective qualities. IF you want to go darker, there are natural options like hemp. Or, you can decide not to dye your hair at all and favor wigs, clip-ins, or your natural hair color.

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