How Long Can You Keep Mixed Hair Dye?

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Whether you just want to cover up a few frustrating hairs, or if you want to entirely change your appearance, hair dye can work wonders. But it can also be a pain to work with! We’ve decided to answer some of the most pertinent questions about hair dye and how you can use it as efficiently as possible.

Today, we’re going to answer a question that many have been asking: “How long can you keep mixed hair dye?” How long can hair dye sit out before going bad?

Permanent hair dye can sit out for 30-60 minutes before going bad, though it depends somewhat on the type of dye we’re talking about. Semi-permanent dye doesn’t get mixed in the same sense permanent dye does, and if properly stored, could last a year.

In this article, we’ll take a look at various types of hair dye and how long they can last once they’ve been mixed. And we’ll also give you a few tips that you can use to conserve your hair dye.


How Long Can You Keep Mixed Hair Dye?

How does hair dye last after it’s been mixed? In order to answer this question, we have to look first at the type of dye we’re talking about, and how each works.

There are two separate mechanisms that hair dye types use to penetrate the hair shaft and alter the natural color of your hair. These are permanent hair color and semi-permanent hair color.

Let’s look at both.

Permanent Hair Dye

Permanent Hair Dye

The most common type of hair dye is the permanent variety that you’ll find available in boxes or tubes at the hair salon or from the pharmacy for at-home use.

This hair dye by Il Salon Milano is a good example:

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Permanent hair dye must be exposed to a hydrogen peroxide (H2O2) developer. This is the same stuff that some use to treat wounds and ensure that they don’t get infected, and it’s the same ingredient used to bleach hair.

When you mix your permanent hair dye with peroxide, it will be activated. Once you’ve mixed the two ingredients, it will soon be rendered unusable.

You can’t un-mix it.

When you mix permanent dye with peroxide, you should plan to use it within thirty minutes. After about 30 minutes elapse, your permanent hair dye won’t be entirely unusable. But it will start gunking up and will be less likely to adhere to your hair properly.

If you keep trying to use the hair dye, you may be able to get some of it to adhere. But you’ll notice that it gets less and less effective over time until there’s no use in even trying to apply it.

You’ll end up with a messed-up, uneven dye job (but who knows, maybe your weird hair will be the new viral Tik Tok trend).

This is why you typically have to be quick when you’re dyeing your hair at home.

When you mix permanent dye with peroxide, you should plan to use it within thirty minutes. After about 30 minutes elapse, your permanent hair dye won’t be entirely unusable. But it will start gunking up and will be less likely to adhere to your hair properly.

If you don’t feel like you’ll have enough time to dye your hair on your own before the dye starts going bad, then you should likely visit a salon so that you can get it done in time.

If you use dye that is losing its effectiveness, you also run the risk of ruining the hair dye that you’ve already applied.

Semi-Permanent Hair Dye

Arctic Fox Semi Permanent Hair Dye

Semi-permanent dye, like the Arctic Fox hair dye shown above, functions differently. It doesn’t get mixed with developer the way permanent dye does

Instead of mixing the dye with peroxide, semi-permanent hair dyes can be activated by the ambient oxygen in the air. You’ll have to handle them even more carefully.

A lot of the time, you’ll find that semi-permanent hair dye comes in airtight containers that may be resealable. If a semi-permanent dye’s container is resealable, it will last a long time, potentially a year.

You should minimize the amount of time that you expose the dye to oxygen if you want to be sure that it will last as long as possible after being mixed.

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How Long Can Hair Dye Last?

In case you don’t mix your hair dye and you’re saving it for future use, you may be wondering how long the dye will retain its potency.

While unmixed dye will last far longer than dye that has already oxidized upon exposure to the air or to peroxide, it won’t last forever.

In most cases, hair dye will last for about two months after you purchase it. That said, this depends on the kind of dye that you get your hands on. As always, you should check the packaging that you got your hair dye in to determine how long it will last.

The expiration date on your package, if you still have it, will be a better indicator than anything we can tell you.

Bland Color

Keep in mind that your hair dye can lose its potency before it reaches the expiration date, depending on the conditions that you store it in. If you want to minimize the risk of your hair dye oxidizing, ensure that you store the package in an airtight container.

In fact, you may want to get your hands on two airtight containers. This will ensure that the dye and the developer don’t end up mixing with each other. If one of the packages fails and the two end up mixing with each other while in storage, you’ll have wasted your money on the extra dye regardless.

Another thing that you’ll want to do to allow your hair dye to retain as much of its effectiveness as possible is to store it in a dark place where it won’t be exposed to sunlight.

Too much sunlight will generate heat that can potentially ruin the hair dye, diminishing its ability to stick to your hair.

What Happens if You Use Old Hair Dye?

You never want to use hair dye if it has expired, though you may be wondering exactly why that’s the case. The most obvious reason to avoid using expired hair dye is that it won’t stick to your hair.

You’ll go through the motions of dyeing your hair without getting any of the results you’re looking for.

If the hair dye has only recently expired, then it may stick somewhat to your hair, but you may notice that the color has changed from what you expected.

While this may not be a complete disaster, the hair dye may not end up giving you the kind of effect you wished to create.

You’re rolling the dice!

In some rare cases, your skin may have an adverse reaction when it comes into contact with expired hair dye. The scalp has some of the most sensitive skin on the human body, so you want to avoid damaging it with products that have gone bad if possible.

While there are some times where expired hair dye may work. But it’s typically not worth the risks you’re taking when you use it on your hair.

Undoing hair dye with new rounds of bleaching will dry out your hair, and you’ll be left trying to hydrate your hair, fix the damage, and get things looking good again.

Stick to the fresh stuff!

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Written by Kayla Young

Kayla is the founder of LuxeLuminous. She has worked professionally in the tanning industry for years. She has been interested in esthetics since childhood, and has tried every hair, skin, and makeup product ever produced (more or less).