What happens if you leave hair dye in too long

What Happens If You Leave Hair Dye in Too Long?

Ever wonder what you might look with a drastically different hair color? I’ve played that game before, feeling those soft and silky hair samples in front of the hair dye boxes. Fun as it is to fantasize about new hair colors, we have to be practical.

I’m not saying you shouldn’t go for pink if your heart is in it, but there’s much more to it than simply grabbing a box of hair color and slathering it on top of your tresses. One thing you need to know is that the color you see on the box (and even on those silky sample strands) might not be how your hair turns out.

Another thing… those boxes sure do make it easy, but they often have some surprising ingredients that you might want to think twice about using. There are other ways to get a gorgeous hair color without destroying your strands or spending a fortune at the stylist.

Perhaps you got into an argument with your boyfriend over the phone, or you got sucked into those episodes of your favorite show and lost track of time. Whatever the reason, you might be asking yourself what happens if you leave hair dye on your hair for too long? Please, keep reading to find out!

What Happens If You Leave Hair Dye in Too Long?

If you leave hair dye in too long without rinsing your hair after the specified time, you may end up with a color that is darker than the one you wanted, or worse, over-processed and brittle hair that might look unnatural, also known as a wig effect.

Your hair won’t fall off, but it’s not a good situation to set it and forget it when it comes to hair dye. Follow me and I’ll help you make sense of this situation no matter what kind of dye or color you might have used, plus I’ve got tips for how to handle it if you do forget to time things just right.

Not knowing what dye you have, I can’t say for certain what will happen. It all depends on which type you’ve used, so I’ll give you a rundown of the possibilities that could unfold.

What happens if you leave semi-permanent hair dye in too long

■ If the Hair Dye Is Semi-Permanent

My best friend had an experience with semi-permanent hair color. She had bought a new color and enthused how psyched she was to try it out. I told her to send me photos after she finished. That was a Saturday around mid-day.

When it reached the evening and I hadn’t heard from her, I called her up to see how it went. I got the story of my life!

Apparently, she put the semi-permanent dye in her hair and then set about passing the time. I should mention that she’s getting married soon and she was completely occupied with the planning. She started tinkering with the seating arrangement chart, then got sidetracked by another task. One thing led to another and suddenly, she realized that over 2 hours had elapsed since she’d put that dye in her hair.

Upon realizing her mistake, she ran to look in the mirror and thankfully, her hair was all there. The dye dried into her hair and became wet again when she washed it out. And her hair stayed on her head when she washed it out.

Why was her hair ok despite her losing track of time? Because it was semi-permanent dye. Semi-permanent dyes don’t have things like peroxide and other damaging chemicals in them. While you should follow the directions and wash it out when time is up, if you space out or even pass out, your hair should be fine, but take it with a grain of salt.

Semi-permanent dyes only deposit color on the external layer of your hair strands. There’s no change to the internal molecular structure. So, while I don’t advise you leave it on longer than the recommended time, if you do for some reason or another, you’re not going to have all your hair fall out.

■ If the Hair Dye Is Permanent

Permanent dye is an entirely different story though. You don’t want to forget about this one being on your head. Permanent dyes have strong chemicals. They draw up the cuticle of your hair shaft to let the pigments do their thing.

Leaving it on longer won’t give you a darker tone if that’s what you’re after. So obey the rules of the dye. Otherwise you’ll sacrifice its resilience and luster, and what is hair if it isn’t strong, healthy, and shiny? You don’t want to look like one of those corpse-like things people put out in their yards around Halloween. That straw hair is not a good look on anyone, except maybe a scarecrow (or a Halloween prop of course).

What happens if you leave black hair dye in too long

■ If the Permanent Hair Dye Is Black

Going for a seductive black permanent hair dye? If you leave it in too long, nothing happens because it will still come out black. What? You think leaving it on longer is a good thing? Nope, doll. Don’t.

Let’s take for example those men’s dyes that promise 5 minutes and poof! No more grays. Let your man use that and tell him to leave it on longer. When he washes that off, it won’t cover grays any better than following the instructions. Instead, his hair will come out too dark and look fake, like he’s trying not to look like his grandpa.

Anything that bleaches your hair is another story though. You do NOT want to tango with that. I’ll get into that further down so keep reading!

What happens if you leave red hair dye in too long

■ If the Permanent Hair Dye Is a Reddish Tone

Red is a bit tricky. They don’t always take well which is why a trip to the salon might be in order if you want to go reddish. Depending on your natural hair color, if you leave it on longer, it might make it darker. In that case, you should apply it to your ends where it’s lightest first and then go for those naturally darker areas closer to your roots. Some of you may have the opposite situation though where the lighter parts of your hair take well to the red and much more quickly.

Again, your hair isn’t going to fall out at the roots with reddish tones, but you might not get the results you were hoping for. Either it will come out too dark or in some cases, it just might not even take at all.

What happens if you leave blonde hair dye in too long

■ If the Permanent Hair Dye Is Blond

And now, what you’re all probably dying to know (or should I say “dyeing” in this case), what if you leave permanent blond hair dye on your hair for too long?

This isn’t a good situation, but most box dyes are designed to deactivate after about 45 minutes. Even if you went over an hour, it wouldn’t be ideal, but you’d still have hair on your head. Will you like that hair anymore though? Probably not.

It all depends on whether or not you’re using a bleach-blond dye over a regular one. If it’s a bleachy one, you’re going to have significant damage to the ends. Don’t try to dye over it or take any drastic measures if this happens to you. I’d recommend calling your stylist and taking stock of the situation first.

What happens if you apply a dark permanent hair dye over bleached hair

■ If You Apply a Dark Permanent Hair Dye over Bleached Hair

See, if you try to correct things yourself, you could make them even worse. When you pile on color to hair you’ve lightened or bleached, that hair is more porous so it’s not going to be as responsive to the dyes you use.

One of two things will happen here. You’ll either have hair that is darker on your tips and lighter at the root. That’s not awful, but you don’t want to chance the other outcome which is the potential for it to turn a murky green or blue. Hair that’s been stripped out of natural color needs the underlying tones added back in before you can play with darker colors.

It’s a very tricky process to master, one that is best left up to an expert colorist. After all, the more you dye your hair, the more you’re subjecting it to damage. This is especially problematic if you’re using a permanent dye. So, put down the dye and call your colorist pronto. A pro can sort this out and save your hair color and hair health though they may make you promise to never ever torture your hair like that again. Darkening light hair is something an expert can and should do. Don’t try to take it into your own hands or you’ll only make things worse.

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

Hairstylists will tell you the most common mistakes they see from their clients. One of them is that people assume that the at-home hair color they’ve selected will come out looking just like it does on the model on the box.

It’s nothing more than good advertising. You see the beauty on the box and you think, “Wow! I could look like that too!” Don’t forget that there’s such a thing as Photoshop that allows the designers to edit and enhance. It’s all a clever show. Even on the part of the box that shows you what your hair could look like after using the dye isn’t the best indicator of how your hair is going to look.

Your hair might be the same color as the examples on the box, but if it’s more porous, you’ll have different results than someone with healthier hair of your same natural color.

Oh, and those lovely silky strands of sample hair that we love to touch in the stores? I probably don’t need to tell you that it’s fake hair, but did you know that it is white fake hair before it is hit with the hair dye samples? Yup!

A good golden rule to follow if you’re dyeing your hair at home is to consider how dark your hair is and estimate it about 3 levels lighter than your current shade when you’re going for a lift. Got dark hair and long for a platinum blonde? That’s not going to happen, at least not successfully at home. If you really want to go from dark to light, you’d better save up for a trip to the salon to have it done professionally.

If your hair isn’t holding the color from too much dyeing or washing, you might want to try using a protein filler. It helps lock in color for a bit longer, especially those permanent ones. This is a great solution if you don’t want to subject your hair to more damage. And believe me, you don’t. Because the more damaged it is, the sadder you’ll be.

Chemicals = damage. You need to be careful about what you use and how often you use it. Going for products that don’t contain harsh chemicals is a better way to color your hair. But if you can’t lock anything into your strands, you might just want to make an appointment at your salon and get an expert’s opinion. Once you fix your hair, you’ll have more options.

Speaking of fixing your hair, that’s where you should begin if you’ve accidentally damaged it by leaving hair dye in for too long. Here’s what you should do to bring your hair back to life.

How to repair your damaged hair after leaving your hair dye in too long

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

Again, I have to remind you not to freak out. 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

One great solution for pampering and nourishing your hair is using coconut oil. You should apply it twice weekly, put a shower cap on and a towel atop your pillow and get some sleep. Extra virgin olive oil will also work if you don’t have coconut oil. For both oils, you’ll want to warm them up. But don’t apply it to your hair while it’s too hot. Let it get to a gentle warm temperature and then slather it on. If you don’t want to leave it on overnight, you should at least wait an hour. Unlike dye though, leaving nourishing oils on your hair for longer won’t cause problems.

Another thing you must avoid is using your hairdryer, flat iron, or curling iron for about 30 days (2011 study). These things cause lots of damage on their own and you’ll only be making the damage you’ve already incurred worse. Even with a heat protectant spray (which you should ALWAYS use when using heat tools – no exceptions!) you need to bring your hair back to proper health. So put those tools away for the next month.

Spoil your hair with absolute love. And eat right and drink plenty of water. Tackling it from the inside will help it heal from the roots.

Above all though, follow the directions on your hair dye!

I can’t stress that enough. If you’re going for something similar in color to your natural color, you should be fine with coloring at home. If you want something different, get it done in a salon first by an expert. This will prevent unnecessary damage and sorrow over bad hair days, I promise.

When washing your hair, take care to be gentle. That means using a moisturizing shampoo that is free of sulfates (as mentioned in this 2015 study). Your conditioner should also be free of sulfates and good for moisturizing damaged hair.

And sorry to be the bearer of bad news, but if you damaged your hair from overdoing it with the dye, you’d need to cut off the ends. Depending on how bad it is, your stylist may need to lob off more than an inch. This might be disappointing if you’ve been trying to grow out your hair, but leaving fried and damaged hair isn’t a flattering look for anyone. It will continue to split up the shaft and then you’ll have no choice but to cut off even more than you expected.


So basically, leaving hair dye on your hair for too long won’t make it fall out. With a semi-permanent dye, it may make your hair look fake in color but because it lacks harsh chemicals, it won’t ruin your hair. Permanent hair dye is the one to watch out for, especially when doing bleach blonde shades.

Always set a timer when you dye your hair so that when you busy yourself with chores, snacks, wedding prep, reading, or even getting lost in episodes of your favorite shows, you know when it’s time to wash it out!


My name is Hajer and welcome to my site. This is my little haven, my outlet, where I can express myself, and show you everything I've learned about makeup, skincare, hair tips, and so much more, as well as the different beauty mistakes I've made so that you can avoid them.

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