What Happens If You Leave Hair Dye in Too Long – Will It Damage Hair?

What Happens If You Leave Hair Dye in Too Long - Will It Damage Hair?
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Have you ever imagined what you might look like with significantly different hair colors? Most of us have played the game where we touch the silky, smooth hair samples on the front of the hair coloring boxes. As enjoyable as it is to think about different hair colours, we must be realistic.

You risk getting a color that is darker than the one you intended if you leave hair dye in for longer than recommended and don’t rinse it out.

Perhaps you got into a phone fight with your lover, or you got drawn into the latest episode of your favourite programme and lost count of the time. What will happen if you leave hair color on your hair for a long time? This question may be on your mind, regardless of the reason. To learn more, please keep reading about whether leaving hair dye too long will damage hair!

What Happens If You Leave Hair Dye in Too Long?

What Happens If You Leave Hair Dye in Too Long - Will It Damage Hair?

Hair dye has a tendency to harm hair if left on for an extended period of time. However, this depends on various factors including, the hair thickness and the dye type.

Before attempting any DIY hair dyeing, you should be aware of all these variables and other hair dyeing-related aspects. In this guide, you will learn:

  • How hair dye works
  • Harmful ingredients in hair dye
  • How long you should leave hair dye on
  • Things to avoid when coloring your hair
  • Frequently Asked Questions on hair dyes
  • What happens when you leave hair dye for too long
  • What you should do if you leave your hair dye for too long

Continue reading to learn what happens if you leave hair dye in your hair for too long and to get answers to other hair dyeing-related questions.

Read More: How Long Does Hair Dye Last – When It Fade Completely?

Understanding How Hair Dye Works

Whether you use a permanent or semi-permanent hair dye will affect how the dye works.

Non-Permanent Hair Dye

Non-permanent (also known as semi-permanent) hair dye covers the hair strands with a new color without penetrating the cuticle and altering the molecular structure of the hair.

The absence of chemicals like ammonia and peroxide, which penetrate the cuticle and alter the natural pigmentation of the hair strand, is a factor in their inability to penetrate the cuticle.

Permanent Hair Dye

Hair dyes that are permanent penetrate the hair cuticle and bond with the hair by altering the molecular structure of the hair cortex. Permanent hair dyes cannot be washed out like non-permanent hair colors can.

That does not preclude you from altering them, though. Essentially, you can change the first permanent coating up to three times using darker or lighter hues.

What Are the Consequences of Leaving the Dye on Your Hair for An Excessive Amount of Time?

You run the risk of getting a shade that is darker than the color you wanted or, worse still, brittle, over-processed hair that may look unnatural, a condition known as the “wig effect” if you let the hair dye sit in your hair for longer than the recommended amount of time without washing it after the recommended amount of time has passed.

Even while this won’t cause your hair to fall out, it’s not a good idea to colour your hair and then leave it alone on your hair for a long period of time. If you continue reading, we will educate you on the consequence of this issue no matter what sort of dye or colour you could have used, and we will also give you some pointers and insights on how to deal with it in case you don’t get the timing just right.

Because we don’t know what kind of dye you have and we can’t tell you for sure what will take place. Let us give you an overview of the various possibilities so you can see how it all depends on the type of dye you used.

Harmful Ingredients in Hair Dye

Not all hair dyes are safe to use. Some dye products from phony manufacturers might include dangerous chemicals that do more harm to your hair than good.

Picking products with components that would enhance the quality of your hair can be made easier if you are familiar with these harmful ingredients. Examples of these harmful ingredients include:

What Happens If You Leave Hair Dye in Too Long - Will It Damage Hair?


Permanent dyes frequently contain ammonia to enable dye penetration into the cortex of the hair by passing through the hair cuticle. Even though it is perfect for penetrating the hair cuticle, overusing it can damage or dry out the hair. Additionally, too much exposure to ammonia can irritate the throat and cause respiratory issues.

Para-Phenylenediamine (PPD)

In both permanent and semi-permanent dyes, para-phenylenediamine (PPD) is present. Despite the product’s effectiveness, severe side effects, particularly in those with scalp allergies, can occur.

It makes the skin more sensitive and sets off allergic reactions. This chemical can have negative effects on respiratory and cardiac health when exposed for an extended period of time.

Titanium Dioxide

Some hair dyes frequently contain titanium dioxide, but prolonged exposure has cancer-causing effects. To protect yourself from the potential carcinogenic effects, it is best to avoid this chemical product.


People with extremely sensitive skin should avoid using resorcinol because it can cause allergic reactions. Additionally, inhaling the chemical accidentally can result in abdominal problems because of how highly combustible it is.

How Long You Should Leave Hair Dye In

Many hair dyes include usage guidelines that explain how long you should leave the dye on your hair. However, the majority of dyes take 30 to 45 minutes to take effect, so you should only leave them on your hair for that amount of time.

It’s important to note that this timing might not be suitable for everyone. For example, if the hair is thick, some individuals might need a longer period. What determines how long hair dye can be left on? The main factors are listed below.

Hair Color

Each dye is packaged with a few illustrations of the anticipated dyeing effects. The process might go more quickly if the results you want are similar to the color of your hair. For instance, the process will go more quickly if your current hair is brown and you are using a light brown dye than if it is black.

Hair Thickness

Thin, medium, and thick hair strands make up the three main thickness categories. The quickest and lightest hair to change color is that which is thin. If your hair is light in color, dying it should take the shortest possible time, i.e., 30 minutes, to avoid damaging it.

Medium hair has a medium thickness, and it’s the most common. The dyeing process can take 30 to 40 minutes to change the color.

The thick category of hair strands is the last to be dyed because it takes the longest. If you have thick hair, you might also need more dye products for great results.

Hair Porosity

The ability of hair to retain moisture for a predetermined amount of time is referred to as hair porosity. There are different levels of hair porosity. A few hair strands dipped in a cup of water will quickly reveal the porosity of your hair.

If the hair sinks in less than five minutes, then your hair is highly porous. If your hair is still floating after five minutes, it has a low porosity, which makes it more dye-resistant.

So, highly porous hair requires the least time to dye, but you may need an average of 45 minutes if your hair does not readily absorb moisture.

What Happens If You Leave Hair Dye in Too Long?

When hair dye is left on for too long, many scenarios are possible.

Semi-Permanent Dye

When you get busy and forget to rinse in time, there’s not much to worry about because semi-permanent dye does not contain strong chemicals. However, leaving the dye on for an extended period can bring a darker shade than your expectations.

Permanent Dye

Permanent dye contains strong chemicals, so you can easily land in trouble for forgetting to rinse in time. When the dye remains on hair for long, the dye absorbs moisture in the hair follicles, leaving your hair dry. In particular if the strands are thin, excessive hair dryness can cause the hair to break.

What Should You Do If You Leave Your Hair Dye in Too Long?

When you accidentally dye your hair too long, there are worthwhile solutions to take into account. Here are some of them:

  • Avoid heat styling solutions such as flat iron to avoid causing further damage to the hair strands
  • Apply hair conditioner to keep your hair moisturized
  • Decrease the hair washing frequency to prevent hair loss
  • Seek professional help if you find it hard to restore your hair

Why Leaving Hair Dye for Too Long Won’t Give the Color You Opt For

The most typical errors made by clients are listed by hairstylists. One of them is the misconception that people have that their at-home hair color will turn out exactly like it does on the box’s model.

It is simply effective advertising. You see the beauty on the box and you think, “Wow! I could look like that too!” Keep in mind that Photoshop exists and that it enables editing and enhancing for designers. It’s all a clever show. Even the portion of the box that depicts what your hair might look like after using the dye isn’t the best predictor of how your hair will turn out.

Even though your hair is the same color as the ones in the box examples, if it is more porous, the results will be different from those of someone with healthier hair of the same natural color.

Oh, and those gorgeous, silky strands of test hair that we adore touching in the stores? You probably don’t need me to tell you that it’s fake hair, but did you know that it was white fake hair before it was dyed with the hair dye samples? Yup!

Consider how dark your hair is and estimate it to be about 3 levels lighter than your current shade when you’re going for a lift. This is a good golden rule to follow if you’re dying your hair at home. Have you ever wanted platinum blonde hair but have dark hair? That won’t take place, at least not successfully at home. You should set aside money for a trip to the salon so you can have it done professionally if you really want to go from dark to light.

You might want to try using a protein filler if your hair isn’t holding the color due to excessive washing or dyeing. Particularly with permanent colors, it aids in slightly longer-lasting color retention. If you don’t want to further harm your hair, this is a great solution. And believe me, you don’t. You will feel more dejected the more damaged it is.

What Happens If You Leave Hair Dye in Too Long - Will It Damage Hair?

Things to Consider

You can dye your hair if you don’t get time to visit a salon. Although it’s simple, there are some errors you should avoid if you want to increase safety and achieve the best outcomes. Here are some of them:

Your choice of hair color is the first step toward a successful hair dyeing procedure. Do you prefer permanent or semi-permanent hair dye? And how many boxes will you require to achieve your goals?

Which dye color do you need, better yet? To select the best dye for your hair color and texture, it is critical to understand the various dye options.

  • Washing Your Hair – Washing your hair immediately before dyeing may affect your scalp, especially if you have sensitive skin. Your scalp is protected by unwashed hair, so irritation doesn’t develop quickly.
  • The Patch Test – If it’s your first time using a specific dye, a patch test is imperative. Only a small section of your hair should be used to test the dye at first. You can dye the rest of the hair if everything goes smoothly and there are no irritants.
  • Applying the Dye – To ensure even results during the dyeing process, a systematic approach is needed. If at all possible, separate the hair into four sections so that you can dye each section separately.
  • Timing – It’s essential to follow the manufacturer’s instructions regarding the processing time. You ought to wait 30 to 45 minutes before rinsing, on average.

How to Repair Damaged Hair After Leaving Hair Dye in Too Long

I’ve got to say it again: don’t panic. Your hair isn’t going to fall out. It will be much weaker and considerably more fragile though so you’re going to have to baby it back to good health.

That means you need to:

  • Pamper and nourish your hair
  • Avoid heat styling
  • Be gentle when caring for your hair
  • Cut off those damaged ends

Coconut oil is a fantastic way to treat and nourish your hair. You should apply it twice weekly, put a shower cap on and a towel atop your pillow and get some sleep. In the absence of coconut oil, extra virgin olive oil will also work. You should warm up both oils. On the other hand, avoid using it on your hair when it’s too hot. Apply after it has warmed up to a comfortable temperature. Wait at least an hour before turning it off if you don’t want to leave it on all night. Unlike dye though, leaving nourishing oils on your hair for longer won’t cause problems.

For about 30 days, you should refrain from using your hairdryer, flat iron, or curling iron (2011 study). These things already cause a great deal of harm, so continuing to do so will only serve to exacerbate it. Even with a heat-protectant spray (which you should ALWAYS use when using heat-generating devices; no exceptions!) you need to bring your hair back to proper health. So store those tools away for the upcoming month.


Too much time spent letting your hair sit in hair dye could harm it. You should only leave most dyes in for 30 to 45 minutes. Don’t worry if you leave it unattended for too long. To prevent further harm, heed the above advice.

Frequently Asked Questions

Here are four commonly asked questions to put your mind at ease if this is your first time considering hair dyeing:

Should I Visit a Professional Or Color the Hair Myself?

You can consult a licensed professional on the best hair dye for your color. If you need help applying the dye yourself or guidance, the hair expert can help.

Can Dye Damage My Hair?

No, the dye doesn’t harm your hair follicles. However, you can improve dyeing safety by avoiding dyes with harmful chemicals and working with a professional.

Can Hair Dye Cover My Gray Hair?

Yes, dyeing is a great way to cover gray hair. If your gray hair is more than 60% gray, a permanent dye is best.

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