What to Know About Hair Bleach

Medically Reviewed by Jabeen Begum, MD on November 25, 2022
6 min read

Hair bleaching is one of the most popular trends in contemporary haircare. Whether you're looking to go blond, color your hair bright, or simply add some highlights, lightening your locks will require the use of hair bleach. But unlike hair colors, bleaches are more aggressive and can significantly affect the health and texture of your hair.

If you decide to go for bleaching, pay careful attention to the products you use, the process itself, and the duration for which you keep the bleach on your hair. Following the best bleaching practices will help you achieve your desired look while doing the least damage to your hair.

Hair bleach is a chemical agent that lightens your hair color by removing the pigment from your hair strands. It's one of the fastest and simplest ways to strip your hair of color. Once the bleach lightens your hair enough, you can use a hair dye to alter your hair color.

Your hair gets its natural color from the pigment molecule called melanin. Two types of melanin are commonly found in human hair: eumelanin and pheomelanin. While eumelanin is responsible for the black and brown colors of human skin and hair, pheomelanin gives hair a red hue. Hair color changes from person to person because these two melanin types are present in different ratios in different people. Bleaching agents remove melanin from your hair strands to lighten them.

Depending on the strength you need, you can use one of two types of hair bleaching agents. The first, called lightener, is capable of bleaching black strands into brown. The more powerful agent — commonly known as powder-bleach — turns black hair light brown.

The mechanism of bleaching remains the same whether you're using a lightener or a powder-bleach. Most hair bleaching products contain two types of chemicals: an alkaline agent and an oxidizing agent. For example, in lighteners, ethanolamine or ammonia provides the alkaline conditions necessary for lightening, while hydrogen peroxide (H2O2) helps in oxidation. In the case of powder-bleaches, persulfate salts also act as additional oxidizing agents alongside hydrogen peroxide.

While bleaching your hair, first treat your strands with the alkaline agent. This opens up the cuticle of your hair strands and creates a suitable environment for the oxidizing agent to work. Under the alkaline conditions, H2O2 chemically cleaves the melanin molecule and causes them to undergo oxidative degradation. As a result, the melanin pigments dissolve. This makes your hair lighter in color. 

Some people confuse hair bleaches with those used for household purposes. Remember that what you use for cleaning laundry and sanitizing surfaces are either sodium hypochlorite bleaches or oxygen bleaches. It's true that such household bleaches also use the process of oxidation to whiten clothes and surfaces, but they are much more toxic and corrosive than hair bleaches and should never be used on your body.

Many experts recommend getting hair bleached by a professional. Unlike hair colors, bleaching agents penetrate the cuticle layer of your hair, making it more prone to damage. If not done properly, bleaching could severely affect your hair quality. If you still want to bleach your hair at home, use a hair bleaching kit, and follow the instructions very carefully.

Bleaching kits have everything you need to bleach your hair, including instructions, developer, bleaching powder/liquid, and gloves. Keep in mind that different bleaching products often have different usage guidelines, so always follow the instructions included in your bleaching kit.

While there's no universal process for hair bleaching, you may more or less need to follow these steps to get your desired hair color:

1. Mix the developer and bleach together.

2. Apply the mixture to your hair evenly using a brush or comb, while making sure it doesn't get on your clothes or skin.

3. Cover your hair with a shower cap and let the mixture sit on your hair for 15 to 30 minutes. The right amount of time to let the bleach sit depends on:

  • Your hair type
  • Your starting color
  • The color you're hoping to achieve
  • The type and volume of the developer

If you're using a kit, stick to the recommended duration mentioned in the instructions.

4. Once you're ready to rinse out the mixture, shampoo and condition your hair. If there's an extra nourishing conditioner in your bleaching kit, use that too. Rinse once more and wait for your hair to dry. 

5. If the shade that you have got is what you desire, you could follow it up with a toner to even out your hair color. If you plan to use a permanent hair dye, you may have to wait between bleaching and dyeing your hair.

This is what happens to your hair once it's bleached: 

Your hair texture changes. Bleaching — especially if done regularly — can bring permanent changes to your hair texture. You could find your hair becoming drier, thicker, or rougher after frequent bleaching.

Your hair strands swell. Bleaching agents cause your hair cuticles to swell making your hair look more voluminous after a bleaching session.

Your hair color changes. You may find your hair changing color in unexpected ways after bleaching. For example, if your original hair color is black, you may find it turning reddish orange when bleached.

The side effects associated with hair bleaching range in severity. One common issue is the lingering scent of ammonium hydroxide. Bleaching could also make your hair weaker and more prone to breakage.

Bleaching causes 15% to 20% of the hair's protein bands to break. Keratins are the key proteins that make up your hair. So, when keratins break, the hair strands lose their structural integrity and become brittle. 

In addition to minor problems, hair bleaching also poses some serious risks, including:

Scalp burns. Those who use powerful bleaching agents or heat styling tools just after bleaching often face the risk of burning their scalp.

Hair bleach poisoning. Some chemicals in hair bleaches — including ethyl alcohol, ammonium persulfate, and hydrogen peroxide — are highly toxic and harmful to your health. So, if you end up swallowing a bleaching agent or splashing it on your eyes or skin, you could get hair bleach poisoning. Symptoms of hair bleach poisoning include:

  • Diarrhea
  • Slurred speech
  • Abdominal pain
  • Low blood pressure
  • Difficulty in breathing
  • Inability to walk properly
  • Burning pain in the throat
  • Burning and redness in the eyes

Get medical help immediately if you suspect hair bleach poisoning. In case the chemical has come in contact with your eyes, wash your eyes with lots of water for at least 15 minutes. If you find that you have accidentally swallowed the bleach, don't induce vomiting unless suggested by a healthcare expert.

Bleaching weakens hair strands. So, before you try hair bleaching, consider if your hair is healthy enough to handle it. If it's not, avoid bleaching it to lower your risk of hair damage. 

Keep in mind that it could take several bleaching sessions to get a drastic change in your hair color. You may be tempted to keep the bleach on your hair for a long time or plan sessions one after another to achieve your desired results more quickly. By doing so, you could damage your hair significantly. Always tick to the recommended sitting time and plan your sessions a minimum of 14 days apart.

If you find your strands breaking more after bleaching, you could use products with bis-aminopropyl diglycol dimaleate and ceramides, which are known to restore the health of bleached hair.