How long can hair dye sit out without going bad?

woman holds big watch and thinks about dye rest

  • Actually, hair dye shouldn’t sit out for even a minute before you start applying it to your hair.
  • This means that once you mix the developer and the dye, you should immediately apply the mixture to your hair.
  • Because after 45 minutes, the coloring mixture will start to deteriorate. And if you apply the decayed mixture to your hair, you could damage your hair and ruin its color.


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Nothing must distract you when you’re coloring your hair.

Therefore,  once you finish mixing the dye and developer to make your coloring mixture, you should immediately apply it to your hair. You can’t let the dye sit out at all. 


Besides, why would you want to let the dye wait?

  •  If you think the color will be more intense because you let the dye sit for longer , you’re wrong. Coloring mixtures don’t work like that.
  •  If you think that by letting the dye sit for longer, the chemicals will damage your hair less  because they would lose strength, things don’t work that way either. Because the longer you let the chemicals sit, the more they decay and cause more damage.


leave the prepared hair dye at rest

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The moment you finish mixing the dye with the developer, don’t waste time. Start applying the mixture to your hair. No excuses and no distractions. And no last-minute emergencies.


What if you’re about to apply the dye, and an issue requires immediate attention? And you know the dye will be sitting for even just ten minutes? Throw the dye away. Because a dye you leave to sit out can ruin your hair.

Why is that? That’s what I’ll talk about next.


Never let the dye sit for even five minutes but rather apply it immediately

freshly applied hair dye

And just so you understand the importance of this statement, let’s talk a little about chemistry. Permanent hair dye is made up of two elements: the color, which contains ammonia, and the developer or hydrogen peroxide.

When you mix the color and the developer, a chemical reaction generates oxidation and opens the hair cuticles so that the dye can penetrate the hair. It reaches the core where the color is finally fixed.

Oxidation fixes the color but also protects the hair from dehydration and loss of nutrients.

 Oxidation occurs in the first twenty minutes after mixing the dye with the developer.  So to speak, in the first twenty minutes, the coloring mixture has the greatest penetration and fixing power in the hair.


So  , although the mixture can last up to 45 minutes, it’s vital you start applying it to your hair as soon as you finish preparing it. 

What could happen if you let the dye sit for ten, fifteen, or even twenty minutes and then apply it?


 The coloring mixture will lose strength, so it won’t set inside the hair and your hair won’t change color. You may even have some darker spots. 


In addition, you can expose yourself to scalp burns because the chemicals will have started to decay by then.

That’s why it’s essential you apply the dye immediately after preparing it, starting from the roots.


Let’s say you were about to apply the dye, and your cell phone rang. Your best friend wants to tell you about her latest drama. Since you know you can’t let the dye sit, but at the same time, you can’t immediately cut off your friend’s call, you give her a few minutes of your attention.

You’ve let the dye sit for about fifteen minutes. And you wonder, will you be able to use it? Let’s find out.


How to tell if a dye that has been sitting out is spoiled

word help formed with hair dyed with spoiled hair dye

You already know you shouldn’t let a dye sit out. But you never know what unforeseen events life has in store.

Therefore,  it’s important to know how you can identify a dye that’s ruined because it has been left to sit out. 

  •  If the coloring mixture darkened abruptly , discard it. Because the oxidation is over. Instead of dye, you now have chemical waste.
  •  If the dye has a liquid consistency , discard it. Because now it won’t even work on your hair.
  •  If the dye has a pungent odor , discard it immediately because the ammonia has decayed and is producing vapors that can irritate your eyes or nasal passages.
  •  If the mixture has white foam on the surface , the dye is ruined.



You should use hair dye as soon as you finish mixing the color and the developer. Otherwise, the dye mixture will decay. Then it won’t change the color of your hair, but it can damage it and cause scalp irritation.

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