Facts Checked By Freewill Beauty Experts - Written by Shreya Singh (Pharmacist) on 17th Nov 2020

Is lightening your hair with hydrogen peroxide harmful? 

Is lightening hair harmful?

When it comes to adding that unmistakable sheen to your hair or just changing its appearance, there are only a few things as appealing as a new hair color.

While you may be a pro in knowing about different hair dyes, chances are as a teenager or ignorant college student, you may have considered counting on inexpensive ingredients such as hydrogen peroxide to achieve those luscious blonde or brown tresses of your dreams.

After all, why go to lavish salons and beauty parlors for professional hair coloring, which could often cost you an arm & a leg when you can get pretty much the same results with at-home hair lightening using hydrogen peroxide, right?

But unfortunately, bleaching agents such as hydrogen peroxide can be hard on your strands, making them dry, brittle, frizzy-looking, which starts breaking in the process.

Therefore, in this article, we will be breaking down everything about using hydrogen peroxide for your hair so that you don't end up with a terrible, blotchy dye job!

Thus, before you soak your hair in hydrogen peroxide to go a shade lighter, read on for what you need to know. 

What is hydrogen peroxide? 

H2O2, more commonly known as Hydrogen Peroxide, is a pale blue liquid in its purest form and is slightly more viscous than water. However, the one you find in grocery stores or salons is an artificially synthesized, colorless liquid chemical.

It comes with innumerable uses, as a germicidal disinfectant, as an antiseptic, and as a substitute for bleaching agent.

A concentration as low as 3% of hydrogen peroxide is safe to use and is easily accessible in drugstores and grocery stores. However, one should know how much to use it and how long to leave it on.

Owing to its diverse uses for our skin, hair, teeth, nails, and even ears, this chemical has found its way into our beauty cabinets. 

Fun Fact:

The chemical formula of hydrogen peroxide is H2O2, meaning two hydrogen and two oxygen atoms constitute one molecule of hydrogen peroxide. But don't mistake it for water (H2O) with an extra oxygen atom. This chemical compound is nothing like water. That added oxygen makes all the difference! 

Hydrogen peroxide to lighten hair 

It is a well-known hair dye ingredient commonly included in most hair dyes to lighten your hair color along with ammonia, lead acetates, and paraphenylenediamine (PPD).

It is a bleaching agent that alters your hair color by penetrating the strand's cortex (the innermost part that holds the melanin pigment which imparts hair its characteristic color). It also breaks apart the melanin pigment within to strip the dark color off from your mane, allowing a new color to replace it easily.

It is often used to transform dark hair into a lighter color before dying it with another color.

Although it does cause a lightning effect, not without taking your hair's natural oils with it and corroding the strands in the process, which ultimately leads to breakage, frizz, and split ends.

And not to burst your bubble, but dying your hair with hydrogen peroxide is considered a permanent treatment, and there's no way to reverse it until new hair grows out. 

Did you know?

Ever heard of the phrase 'peroxide blonde'? This term is derived from the fact that hydrogen peroxide is used as a bleaching agent to lighten hair by stripping the natural pigment from your hair shaft before dying it in another color. 

Hydrogen peroxide and hair damage

A concentration of 3% of hydrogen peroxide is generally considered safe to use on your skin and hair, but it could still cause some adverse impacts if not used properly.

And it's worth mentioning that bleaching does have some advantages: this process plumps up your hair shafts, making your tresses appear thicker and fuller. Moreover, if you're light-skinned and experiencing thinning hair, bleaching can cover up the distinction between your hair and patches of bare scalp, but not without having negative impacts on your mane.

Below are some of the adverse effects hydrogen peroxide hair bleach can have on your mane and scalp if misused:

Hair loss: 

Hydrogen peroxide is a kind of oxidative hair dye. It means that it strips the natural color from your hair by reacting with the cortex through the process of oxidation and thus, resulting in new hair color.

And as treatment with hydrogen peroxide causes a more permanent effect than other temporary hair dyes, it also leads to oxidative stress for your hair strands, which ultimately weakens and ages your hair and causes them to fall off.

According to a 2018 study published in the Journal of Dermatological Science, many patients often visit dermatologists complaining of hair dye induced hair loss with increased usage. The study further remarks that this is because of its cytotoxic (toxic to living cells) effects and the ability to cause oxidative stress.

It is one of many reasons to limit hair dyes' frequent usage and pay attention to instructions and warning labels while performing a hair dye treatment. 


Dermatitis is the general term used for indicating inflammation of the skin. And although you can use it on your skin as a disinfectant, frequent exposure to hydrogen peroxide and longer durations may result in rashes or allergic reactions.

Your scalp can likewise experience irritation and discomfort while dying your tresses with hydrogen peroxide. Therefore, it is advised to use this chemical with caution by preventing your hairline from coming in contact with the peroxide and making sure that it stays in your hair for as little time as possible.

A study published in the National Center for Biotechnology Information (NCBI) discovered results suggesting that hydrogen peroxide and monoethanolamine are the key ingredients that cause hair dye-associated dermatitis. Eeks! 

Scalp burns: 

There is another serious issue that can potentially be caused by hydrogen peroxide. The improper use of this chemical could also result in scalp burns.

According to an NCBI study, caustic chemicals like hydrogen peroxide can be the primary cause of chemical burns on the scalp. The study further mentions that a caustic reaction can often lead to irritant dermatitis, superficial chemical burns, and deep burns depending on how incorrectly one uses the chemical and how long it exposes its scalp to the harmful ingredient. 

Damage to the hair cuticle: 

When using such harsh chemicals on your mane, it's a no brainer that it could damage your hair cuticle ( the outer layer of your hair).

As the chemical raises your hair's outer cuticle to enable the bleaching agent to penetrate fully, it's repeated use can permanently cause your hair cuticle to remain extended, allowing the rapid and continuous loss of moisture from your hair strands. This permanent cuticle damage ultimately leads to breakage, split ends, and frizzy looking hair.

And it's worth mentioning that bleached hair is likely more porous and thus more susceptible to other chemical and non-chemical hazards. These include everything from heat styling and blow-drying to the effects of sun, rain, and wind. 

How to safely lighten your hair with hydrogen peroxide? 

When it comes to bleaching or lightening your tresses, your safest bet would always be to approach your nearest salon and let the professionals do the job.

However, if you decide to go lighter, it is still possible to safely dye your hair with hydrogen peroxide at home. Just follow these preventive measures to ease away the potential damage and keep your hair healthy, hydrated, and looking its best: 

  • It is advisable to limit the use of hydrogen peroxide on your tresses to not more than once in 6 weeks as the damaging effect of bleaching agents on your hair's protein structure is intensified each time the process is carried out.

    In other words, the more often you'll bleach or highlight your hair, the more damaged it will be. 
  • Aftercare is as much important as the procedure itself. Therefore, always make sure to take deep conditioning treatment after using any form of hydrogen peroxide solution on your hair. A post-shampoo conditioning treatment will plump up and retain the moisture in your hair, making it shinier, manageable, and less likely to snap. 
  • Keep an eye on the 'active ingredients' label to ensure that you're using 3% hydrogen peroxide. A concentration more than that could cause more harm than good to your hair. 
  • Always wash your hair with a shampoo & conditioner specifically designed for your color-treated hair as color-safe products are gentle & do not strip out moisture from your mane, unlike the sulfate-laden ones. 

The Takeaways: 

Hydrogen peroxide hair dyes are one of the most convenient and affordable ways of lightening your hair at home that can provide impressive results, but only if used properly.

But as with many things, using too much hydrogen peroxide on your hair can be hazardous.

And while using this chemical to lighten your hair, always make sure to precisely follow the instructions on the packaging and steer clear of using an undiluted form of hydrogen peroxide on your tresses.