How Long Should I Leave Hair Dye In?

How Long Should I Leave Hair Dye In?

If you are coloring your hair for the first time in your life then there will be a bunch of questions in your mind. You might have fear and doubt in your mind.

A question that everyone has in mind is how long we should leave hair dye in our hair? In general, never leave a hair dye in your hair for less than 30 minutes and more than 45 minutes due to the possible hair damage and undesired colors. This time will depend on lots of factors. 

  • Brand of the dye you are using
  • What effects you want to get after coloring
  • Or you just want roots touch-up?

How long you should let the dye sit in your hair?

The world of hair dyes is extremely vast and you are not familiar and informed about the best hair dye then there is a strong possibility you might fall into a hole. If the purpose behind coloring hair is to get dark hair, then semi-permanent dyes can be the best choice and these dyes will last for almost 15 to 20 shampoos. One thing should be clear whatever dye you are using lasting time will depend on several times you shampoo your hair. 

If the purpose behind coloring is to lighten the hair color, then permanent hair dyes are the best. This dye will last for almost 20 days before the roots start to show up again. 

What the coloring process is?

The coloring process includes chemicals in the shape of a developer, ammonia, and hydrogen peroxide. These chemicals contain an alkaline component that helps in opening the cuticles so that a dye can easily penetrate and desired results can be obtained. Hydrogen peroxide generally changes the color of the pigment in the cortex of hair fiber. The time taken by your hair to develop a new color is called “Processing Time”. This color processing time for standard hair is normally 30 minutes. This time can vary depending on the color you want to achieve and the porosity of your hair. 

During the coloring process in the first fifteen minutes, the product will open up the cuticles so that color can penetrate the cortex. In the next fifteen minutes, it will deposit the new color molecules to hair. 

Amount of time the color stay in hair will depend on color type

Color processing time will be different for different types of hair. When the color at the roots is darker than the rest of the hair color, then processing time for the roots will be more. Processing time will also be influenced by the density of your hair. For denser and heavy hair coloring near the roots will take less time and coloring at the ends will require more time. 

In such cases, it is better to let the color sit for 10 minutes at the roots and then 25 minutes in the middle. Damaged and thick hair more time will be needed by the hair to develop new color. So if that’s the case with you perform a chunk test before applying the hair color directly to your hair. 

If you leave the color for longer periods, then what will happen?

Everyone wants good results from the hair dyes. It can be damaging if you leave the hair dye for more than 30 minutes in your hair. It seems a minor issue, but it’s not the case. It will cause serious damage to your hair. Especially if you are using a permanent dye that contains hydrogen peroxide you will end up in drying your hair. 

In the case of semi-permanent dyes that do not contain a developer, these dyes will stop working after 30 minutes and would not cause any serious damage. So leaving the hair dye in your hair more than the required time will remove the natural moisture from your hair. You might have to use hair care products to get the moisture back. 

How you will apply the color on your hair?

  • Separate the hair layers because you might want to start from the roots.
  • Use a brush to distribute the dye and try to stay as close as possible to the roots. 
  • Covering the entire area of the roots starts from the upper layer and then moves to lower layers.
  • After covering the roots with dye wait for at least 20 minutes.
  • After 20 minutes start applying the dye to the rest of your hair. 
  • After covering the middle and ends again wait for 10 minutes. 
  • After these ten minutes, you can rinse your hair.
  • For washing, cold water is a good option and it is not necessary to use the shampoo. 
  • Under shower start massaging your hair and keep doing this until the water that is rinsing from hair becomes transparent.
  • Now apply a conditioner that usually comes with hair dye. 
  • Probably after doing everything right, you will get the desired results. 


Typically dyes that contain ammonia required only 30 minutes for complete processing. It has been discussed in detail about the color processing time. We can conclude that the normal time for leaving a hair dye in your hair is between 30 to 45 minutes. If you leave it for more or less time you will probably not get the desired hair color. 

Leaving hair color for more than 45 minutes will cause serious damage to your hair. Your hair might become dry and you will have to use oils or conditioner to get the moisture back. It is said that semi-permanent dyes might stop working after the 30 minutes but that’s not the case with permanent dyes. Types of hair and density is also a factor in color processing time. For thick and denser hair processing time will be more. So it is better to wash out the dye after 30 minutes otherwise, it would cause more damage than good. 

Efforts have been made to get the information as accurate and updated as possible. If you found any incorrect information with credible source, please send it via the contact us form
Sky Hoon
Hair Lover, Idea Starter. He started HairQueenie, which is ranked #27 in the FeedSpot Top 40 Hair Care Blogs and mentions in ManeAddicts and Tempest. Hair is not everything but something. He started Hairqueenie to share great hair products. Over time, he found there are more value to share answers to hair problems that cannot be found easily.
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