As a result of oxidation, bleach strips your hair of its pigment. The only way to lighten your hair is to use a bleaching (or oxidizing) agent.
Bleaching agents most commonly used are hydrogen peroxide and ammonia. Separately, they are unstable and slow to lighten the hair, so they are often mixed together. Manufacturers who promote their products as being ‘hair-friendly’ by using ‘peroxide-free’ labels are misleading users—because these mixtures may not contain peroxide, but they may contain another oxidising agent, which can be just as damaging.
How Can You Protect Your Hair If You Bleach It?
INVEST IN A HIGH-QUALITY CONDITIONER
Hair strands can easily tangle and interlock when you bleach them. Bleaching raises the hair’s cuticles. To flatten the cuticle, seal the moisture in, reduce knots, and add shine, apply a conditioner after every shampoo. Make sure that you get the best hair bleach for dark hair if you have one.
Gently brush your hair after every wash.
You can minimize the risk of breaking your bleached hair by gently detangling it, starting at the ends and gradually working your way up. Do not pull too hard.