How Long To Leave Bleach On Hair, Plus Other Coloring Tips

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HealthlineSubscribeHow Long Should You Leave Bleach on Your Hair?

Medically reviewed by Cynthia Cobb, DNP, APRN, WHNP-BC, FAANP — Written by Sarah Kester on September 21, 2020

How long to leave on
How bleach works
Dangers of bleach
Other precautions
Aftercare
Home vs. salon
Takeaway

Lusting after lighter hair but don’t want to go the salon route?

You might be tempted to bleach your own hair, which is when you strip the hair of your color to make it lighter.

While this DIY method isn’t recommended by hair professionals, it can be done.

This article will give you advice on how to bleach your hair at home, including how long you should leave it on your hair, and how to avoid irreversible damage.

How long do you need to leave bleach on hair to color it?

Bleaching isn’t a one-size-fits-all process.

How long you leave it on the hair depends on a number of factors, such as your hair color and texture.

Hair color and texture	How long to leave on
blonde hair	15 to 20 minutes
dark hair	30 minutes; it’s recommended you split the process into several sessions
fine hair	10 to 15 minutes; this type of hair will process faster since it has a thinner cuticle layer
coarse hair	30 minutes; this type of hair is more challenging to work with and may require a minimum of two applications

Additional factors that affect how long you leave bleach on, include:

the color you’re hoping to achieve
whether your hair has been previously colored

How does bleach dye hair?

Bleach is called an “aggressive” product for a reason.

It dyes the hair by opening the hair cuticle and dissolving the color (melanin). The longer you leave it on, the more the protein bonds (keratin) are destroyed.

The two most widely used bleaches are ammonia and hydrogen peroxide. Unfortunately, there aren’t many alternative products to help avoid damage.

For instance, Nikki Goddard, a certified hairstylist and makeup artist, says to not be fooled by products with a “peroxide-free” label.

All this means is that another oxidizing agent was used — one that could be even more harmful to the hair.

What happens if you leave bleach on your hair for too long?

There’s a misconception that bleach will work better the longer you leave it on.

The maximum amount of time you should leave bleach on your hair is 30 minutes. Any longer than that and you run the risk of serious damage, including brittle strands.

Other dangers of bleaching

In addition to leaving bleach on your hair for too long, there are other dangers related to using this type of dye.

Your hair could lose all pigment and turn white

Your hair could turn white from the oxidation process, de-coloring the pigment.

Your hair could become weaker and less able to retain moisture

One study found that the hair was significantly weaker after bleaching. Even skin that the bleach had touched was affected.

Bleach has also been known to turn the hair highly porous. This is when the hair cuticles are too widely spaced, making it difficult for the strands to retain moisture.

“Moderate porosity makes the mane look more voluminous and easier to hold curls,” explains Goddard. “However, excessive porosity and dehydration leads to the destruction of the hair shaft and might cause irreversible damage.”

Your hair could lose keratin

One of the last — and most serious — dangers of bleaching is the hair’s loss of keratin, which is a type of protein that makes up the hair.

Without keratin, the hair structure is compromised, making it brittle and difficult to style. Unfortunately, keratin loss is hard to avoid when bleaching.

Are there any other precautions to take?

Before you go the DIY route of bleaching your hair at home, there are three important things to keep in mind:

1. Complete a patch test beforehand

Before dying your hair at home, complete a patch test. You might have an allergy that you’re not aware of.

In 2012, a 16-year-old girl was admitted to a burn unit for a 1 percent full-thickness chemical burn on the nape of her neck from bleaching.

Testing the hair beforehand also determines whether your hair is too damaged for bleach.

“If the ends kink up, look frizzy or frayed, do not lighten your hair,” stresses Kerry E. Yates, founder of Colour Collective and trichologist in training.

“Instead, go find a clear gloss to apply to smooth things out until your ends are cut away and you have more healthy-looking strands.”

How to do a patch test

Patch tests let you see how your skin reacts to a topically-applied substance, such as hair dye, before you use it in a full application.

Here’s how to do a patch test:

Wash your forearm with a gentle, unscented soap and pat dry
Rub a couple drops of the hair dye into a small area on your inner forearm.
Wait 24 hours.
If the skin patch is red, itchy, blistering, or swollen, you’ve had an adverse reaction to the dye and shouldn’t use it.

NOTE: If the test area on your forearm becomes red and irritated before the 24-hour period ends, immediately wash the area with soap and warm water, and don’t use the dye on your head or hair.

2. Read the directions carefully

Always take professional steps, such as wearing gloves and protective eyewear, recommends Vincent De Marco, hairstylist and owner of Vincent Hair Artistry.

And just like in a professional salon, check on the hair for the level of lightness. The first check should be after 10 minutes, says Yates, and then again every 5 to 10 minutes until you hit 30 minutes.

Yates adds, “If the results you want aren’t there after 30 minutes, rinse it out and mix a fresh batch. Apply and follow the same directions.”

Never leave the bleach on your head for longer than 1 hour.

3. Consider your hair type

Some hair types simply can’t withstand the power of bleach. If you have relaxed, straightened, or chemically-treated hair, Yates says to avoid bleaching.

“This product is not for you and your hair will literally turn to dust if you use lightener,” Yates says.

While bleach can be used on curly hair, you’ll want to keep your texture safe by being very gentle. For example, don’t pull on the hair when applying the product.

What’s the best way to take care of hair post-bleaching?

These tips help restore your hair’s health and softness post-bleaching:

use pre-shampoo conditioners 3 days before and after bleaching
do a post-color treatment, such as Olaplex
apply a nourishing hair mask
apply a thermal protector when styling hair with an iron or a blow dryer
wear a lightweight protective spray or serum daily
use a hair conditioner after shampooing
brush the hair gently without pulling too hard
wash hair with lukewarm water to prevent drying out
use a reconstructing product
wait 6 to 8 weeks before bleaching again

Pros/cons of bleaching at home vs. a professional salon

Here are some pros and cons to consider when choosing whether to dye your hair at home or at a hair salon.

Pros of going to a professional salon

They know what they’re doing

It’s best to leave the drastic changes to the pros. For instance, if you’re trying to go significantly lighter — going from dark brown to platinum blonde, for example — it would be best to visit a salon.

Professionals are also familiar with the bleaching process and can guarantee full coverage. If you go it alone, you might end up with blotchy spots and a color that you don’t like.

They can do an after-color treatment

Another advantage of going to a professional salon is that they can do an after-color treatment, which is a great way to prevent damage.

“These treatments are typically applied at the shampoo bowl and offer a strong burst of moisture and nourishment,” says Milciades “Manny” Rolon, owner of My Darling Ivy/Silver Vine Room.

A common post-hair treatment used by hairstylists is Olaplex, which ensures that the hair can’t overbleach to the point of breakage.

Pros of bleaching your hair at home

It’s cheaper

Bleaching at the salon can cost anywhere from $150 to $200. This number depends on the length of the hair, thickness, and current color.

While it’s more expensive, you’re paying for results — you’re more likely to leave the salon with the color you wanted and less damage thanks to their high-quality professional products.

Cons of bleaching your hair at home

You’re handling very intense chemicals

Bleach is an abrasive chemical that needs to be handled correctly.

“Bleach has an incredibly high pH, upwards of 11–12. This high pH can literally blow up the hair if used incorrectly,” says Yates.

You may not know what’s normal and what’s not when it comes to processing

When you get your hair bleached at a salon, they’ll be checking in on your hair to make sure that it’s processing well. They’re also aware of what’s normal and what’s not.

For example, Rolon says that people should be prepared for an uncomfortable feeling on the scalp when bleach is applied on the scalp.

“Those double-process blondes go through a fair amount of discomfort for their hair color.”

Takeaway

Bleaching your hair at home is a tricky process that has to be done right. This includes carefully following directions, wearing protective material, and taking the right precautions.

Most importantly: don’t leave the bleach on for too long. Doing so could cause irreversible damage, which results in brittle strands.

If you need more advice on how to bleach your hair at home, you can always speak to a hair professional.

How we reviewed this article:

SourcesHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Cruz CF, et al. (2017). Changing the shape of hair with keratin peptides. DOI:http://pubs.rsc.org/-/content/articlehtml/2017/ra/c7ra10461h
De Marco V. (2020). Personal interview.
Forster K, et al. Hair bleaching and skin burning. DOI:https://www.ncbi.nlm.nih.gov/pubmed/23766754
Goddard N. (2020). Personal interview.
How to stop damaging your hair. (n.d.).https://www.aad.org/public/skin-hair-nails/hair-care/how-to-stop-hair-damage
Jeong MS, et al. (2010). Significant damage of the skin and hair following hair bleaching. DOI:https://doi.org/10.1111/j.1346-8138.2010.00916.x
Rolon M. (2020). Personal interview.
Yates K. (2020). Personal interview.

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Medically reviewed by Cynthia Cobb, DNP, APRN, WHNP-BC, FAANP — Written by Sarah Kester on September 21, 2020

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