What Happens When you Bleach Your Hair: The Science

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What happens when you bleach your hair

Bleaching should only target the natural color pigment, in reality however, a lot of collateral damage happens and am afraid it’s not good for your hair.

In this article we will look into:

  • What happens when you bleach your hair?
  • Is it bad to bleach your hair?
  • What to do to prevent damage from bleaching

What Happens When You Bleach Your Hair?

1. Lightening of the Hair Color

Bleaching makes your hair a lighter color by oxidizing the natural hair pigment, melanin.

This is done by the help of oxidizing agents such as:

  • Hydrogen peroxide
  • Ammonia

Often times, ammonia and hydrogen peroxide are mixed together because individually, these two are very unstable and somewhat slow in bleaching.

When an oxidizing agent is applied to hair, it changes the light absorption properties of melanin. [1]

This results in melanin only absorbing the highest visible light and the rest is reflected away. This is why bleached hair has a yellowish tint.

The yellowish color you see is the natural color of keratin and since oxidation makes melanin colorless, this color pops.

Depending on your natural hair tone, it can lighten to yellowish, reddish or platinum blond.

This is because bleach reacts easily with the dark eumelanin pigment than with the phaeomelanin, so some gold or red residual color may remain after lightening.

2. Damage to the Hair proteins

Bleaching breaks down the hair protein resulting in weaker hair strands. [2]

To start the bleaching process, an alkaline solution is used for purposes of opening up the hair cuticles, with the aim of accessing the melanin molecules faster.

When this happens though, the oxidizing agent also gets access to whole hair structure resulting in unwanted oxidation of the hair proteins and fatty acids.

This result in weakening or loss of the hair protein and consequently brittle hair that breaks easily.

3. More Porous Cuticles

What happens when you bleach hair?

The hair cuticles are lifted and become more porous when you bleach your hair.

As mentioned above, the oxidizing agent is used in an alkaline solution for purposes of lifting the cuticles and making the hair more porous. This allows the bleaching agent to fully penetrate.

Several other things happen when the cuticles are open:

  • Open cuticles may end up becoming a split ends and eventually break off
  • There is rapid and continuous loss of moisture through the open cuticles leading to dry hair
  • With the cuticles being open, the hair is more vulnerable to damage from the sun, wind and other chemical agents the hair gets in contact with.

Recap; this happens when you bleach your hair

  • The hair absorbs the alkaline solution whose purpose is to open up the cuticle for faster penetration of the bleach.
  • This is followed by an oxidative agent that penetrates the cortex and dissolve the natural hair color (melanin)
  • Depending on your natural hair tone, it can lighten to yellowish, reddish or platinum blond
  • Bleaching also breaks down the hair proteins resulting in weaker hair strands
  • Bleaching the hair changes the hair porosity by making it more porous. It also changes the hair elasticity
  • Open cuticles may end up becoming a split ends and eventually break off


Is It Bad to Bleach Your Hair?

By now you know the answer, don’t you?

Bleaching damages the hair protein resulting in weak hair that breaks off easily. It also raises the hair cuticles making the hair more porous and thus it loses moisture easily.

A lot of caution should be taken when bleaching hair as the bleaching agents cause collateral damage to the hair cuticles and the cortex.

Care should be taken before and after bleaching the hair to minimize the damage that may result from the process.

What To Do to Prevent Damage from Bleaching?

1. Use a bond repairing treatment

A bond repairing treatment is very important to use to strengthen existing bond and reconnect any broken bonds.

Bleaching damages both the outer layer of the cuticle as well as the structural bonds within the hair. This makes them weak and breaks off easily.

This is why a bond repairing treatment is key.

2. Deep condition the hair

Before you bleach the hair, it’s extremely crucial that you deep condition your hair.

In fact, weeks before you bleach, you should get started with regular deep conditioning treatments to prepare your hair to handle the effects of bleach.

Also, long before bleaching, your hair needs to be in a good state overall, thus nutrition and proper hair care is crucial.

About 3 days after bleaching your hair, to restore the broken proteins and repair the cuticles, you also need to deep condition your hair.

Afterwards, deep condition on a weekly basis.  

3. Be gentle, do not over manipulate your hair

Given that your hair is weakened thanks to the bleaching process, you need to very gently with your hair. Consider things like:

  • Brushing your hair gently
  • Not wearing tight hairstyles or using rubber bands for styling as this may make your hair to snap off easily

4. Use a gentle shampoo

Prevent further damage to your bleached hair by opting for gentle shampoos.

Shampoos are known to contain ingredients that strip the natural oils from the hair.

Therefore, carefully select your shampoos. Read through the ingredients to ensure that they do not contain harsh chemicals.

It’s also a good time to re-consider the frequency with which you wash your hair, if you were doing it daily before, you may want to reduce that frequency.

You can also opt for the no-poo method to cleaning your hair as an alternative to using shampoos too often.

5. Keep off heat for a while or use heat protection

Given that your cuticles are raised following the bleaching process, the hair will likely lose moisture fast and therefore exposing your bleached hair to constant heat will only make things worse.

If you use heat for styling then ensure that you use a high-quality heat protectant.

6. Keep your hair moisturized

Your bleached hair will need extra hydration given that it’s bound to easily lose moisture.

Now is a good time to invest in good moisturizing products such as a light-weight hair serum or a good leave-in conditioner.

It’s also important to pay attention to the moisturizing techniques you use. There are several techniques you can use to effectively moisturize your hair.

Check this article on hydration methods for more detail.

BTW, did you know hair porosity plays a key role in hair growth? Take this simple hair porosity test to determine if your hair is HIGH, LOW or NORMAL porosity.

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