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Can You Reuse Hair Dye After Opening It? After Mixing?

A black female wearing semi-permanent hair dye mixed with peroxide that was used on damp hair for half an hour.

“It pays to be frugal.” Many gals live by that motto, even when it comes to their hair dyeing habits. When you’ve finished coloring your hair and realize that you’ve got some leftover hair dye, your first instinct may be to use it later and save some money.

But is that the best idea? Keep reading to find out if your opened hair dye can be reused or if it’s time to get a new box.

Can You Reuse Hair Dye After Opening It?

You can only reuse dye that hasn’t been mixed with a developer. If you’ve opened hair dye and haven’t mixed it with anything yet, you’re 100% okay to close it again and reuse it later. 

Permanent and demi-permanent dyes are the only dye types that require mixing before application. Once you mix the dye with the developer, it’s no longer reusable. We’ll tell you why in the next section. 

Other types of dye, like temporary and semi-permanent dyes, don’t require mixing and are reusable to a point. After using these dyes, you can close them securely and save them for up to 6 weeks. 

But, if you’re coloring your hair with permanent or demi-permanent dye and you know in advance that you have more color than you need, you’ve got one option.

You’ll need to combine equal parts of each ingredient (1:1) in a glass or plastic bowl and use that for your current dye job. Then save the rest for later in the original packaging (unmixed). 

A young black woman wearing expired semi-permanent dye (leftover box dye) to create light brown highlights.

Why You Shouldn’t Reuse Mixed Hair Dye

Before you reuse that old, mixed hair dye, ask yourself, “Is the money you’re saving by reusing the dye worth a hair catastrophe?” Probably not.

Unfortunately, keeping the leftover dye in the refrigerator won’t help either. Here, we’ll get into why you shouldn’t reuse mixed hair dye under any circumstances.

It Won’t Be Effective

A chemical reaction occurs when you add a tube of permanent hair dye to developer – it’s called oxidation. It’s necessary to lift your hair cuticles and deposit a new hair color deep within your strands.

What’s important to note here is that the process only lasts for so long. For hair color, that’s thirty minutes, whether you’ve added that mix to your hair or not.

Once you’ve mixed the two ingredients, apply the dye immediately to your hair and wait the specified time in your instruction packet.

Cute African American female after using hair dye leftovers stored in a dye tube within an air-tight container.

You Might End up With a Different Color

Although the initial oxidation period only lasts thirty minutes, residual oxidation takes place after that period. And this is not the type of oxidation that you want.

There are metals in any permanent or demi-permanent dye, like iron, nickel, and copper. And when these metals are oxidized, wonky color changes take place.

If you use old, mixed hair dye, your hair could turn green! While this effect is less likely to happen to people with darker colored hair, if you have lighter hair – like blonde or white – your hair could start turning green.

You Could Develop a Chemical Burn or Skin Reaction

Even if you usually don’t react badly to hair dyes, when reusing mixed hair dye, you run the risk of developing a chemical burn or allergic reaction. 

Though the symptoms from a chemical burn would almost always be instantaneous, an allergic reaction could happen up to three days after applying the mixture. Symptoms include a rash, burning, sores, or itching, all of which can be painful and irritating.

A black woman with semi-permanent hair color mixed with peroxide applied damp locks for half an hour.

How to Store Unmixed Hair Dye for Later Use

If you’re set on getting multiple uses out of your hair color kit, don’t worry. There’s a way to save it for next time.

After you’ve combined half of each mixture and put it into a plastic or glass container and mixed it with a paintbrush or wooden spoon, follow these steps to store your hair dye.

Note: Never use metal materials like spoons or bowls to mix the hair dye as it can alter the oxidation process.

  1. Leave each ingredient in its original container, and replace the cap securely: The hair dye and developer tubes are air-locked, which prevents the ingredients from expiring quicker than if they were left out. Package these ingredients in the original packaging.
  2. Store your unmixed hair dye in a cool, dark place: Your bathroom closet or cabinet is a great spot to store your hair dye until the next use. Never allow your hair dye to sit near heat or under sunlight, as this can change the dye’s color or cause the dye to harden.
  3. Use the unmixed dye within six weeks: Unopened hair dye has a shelf life of three years, but once it is exposed to air, the oxidation process occurs. Most manufacturers state that you can keep the dye for up to six weeks after opening. They can’t guarantee any efficacy after that period.
A young black woman with light brown highlights created by a semi-permanent dye that has expired.

How to Dispose of Mixed Hair Dye After Use

Like any chemical, you should always dispose of the remnants safely and properly to ensure other harmful reactions don’t occur. The best way to dispose of mixed hair dye is to put it in a hazardous waste container. If you’d rather not do that, there are other alternatives to explore.

We’ll get into some of your options below:

Do: Throw It Away in a Mixed Waste Container

Package your dye up as best you can and toss it in the trash. The goal is to make sure that the dye doesn’t get mixed with other reactors or leak into the ground when the mixture makes it to the landfill.

Don’t: Throw It in the Recycling

Throwing your mixed dye in the recycling bin not only makes everything in your bin unusable, but it can also do some serious harm to the environment!

Do: Share the Extra Dye With a Friend

Do you and a friend use the same color shade? Have a girls’ day of pampering where you color your hair with a friend.

Make it a point to use up every ounce of that dye, so you don’t have any going to waste. You can also give a friend the unmixed ingredients if getting together isn’t possible.

Don’t: Pour It Down the Sink

Pouring your mixed hair dye down the sink can introduce chemicals into groundwater or local watersheds and kill the organisms living there.

If your drains are connected to a sewer system, those chemicals will get into the water supply, and it can be difficult for water treatment plants to filter these chemicals out. This means you and others could end up drinking what you just poured down the drain.

A lovely black girl after utilizing hair dye remnants kept in a dye tube within an airtight container.

How to Tell if Dye Has Gone Bad

If something seems off about your hair dye, it’s probably expired. The first step you should always take is to check the expiration box on your color kit.

If the expiration date has not yet passed, use the following list to confirm if the dye has expired. If any of the following apply, the only solution is to throw it out.

  • The dye smells off. 
  • The dye looks different than it usually does.
  • The ingredients have begun separating (think oil and water).
  • The bottle is leaking, cracked, or open in any way.

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At the end of the day, it’s always better to be safe than sorry when it comes to putting chemicals on your skin or hair. If you’re ever unsure about using opened dye, you can throw it out or consult a professional colorist in your area.

Most colorists won’t mind helping you out. Whether you’re a seasoned pro at dyeing your hair or you’re just experimenting, remember that hair color transformations are supposed to be fun – so have fun!