How Long Can You Keep Mixed Hair Dye? Can You Save Leftovers?

African American female wearing semi-permanent hair dye on her medium brown natural curls.

After coloring your hair, you might be surprised to see just how much dye you have left over. In your mind, you may be thinking, “Can I save hair dye after it’s been mixed for a touch-up?” How long can hair dye last its been mixed?

Before sticking your remaining hair color in the fridge for later, read this article! We’ll look at how long you should hold onto hair dye after it’s mixed and give you tips on how to best deal with dye leftovers.

How Long Can You Keep Mixed Hair Dye?

Once you mix your hair dye with a developer, you’ll have to either use or dispose of it within one hour. Unlike semi-permanent hair dyes, permanent and demi-permanent hair colors are mixed with a developer before application.

Developers contain hydrogen peroxide, which helps open your hair’s cuticle so the dye can deposit its pigments inside your strands. Though this mixture creates long-lasting color, peroxide is incredibly unstable.

As it reacts to the oxygen in the air, chemical changes take place that makes the dye unsafe or ineffective. Read this article to learn more about the dangers of using expired hair dye.

A cute light-skinned black girl after using a DIY hair coloring box dye kit for about half an hour on her own hair.

Why You Shouldn’t Leave Mixed Dye Out Too Long

Leaving your dye out for a while may seem harmless, but the oxidation that occurs will throw off your results and can even ruin your hair. Here are some risks of leaving mixed hair dye out for longer than an hour. 

  • Skin irritation and burns – Although your skin may react to new or old dye, using hair color that’s been left out too long increases your chances of developing allergic reactions and irritation. This irritation can lead to hair loss in the most severe cases, so you should avoid this at all costs. 
    • Hair dye is full of chemicals that must be used correctly for the best results. Some of the ingredients that are most likely to cause an allergic reaction are: 
      • Metallic salts
      • Paraphenylenediamine (PPD)
      • Ammonia
      • Hydrogen peroxide
      • Resorcinol 
  • Your dye can turn green – As the hard metals in hair dye oxidize, they can start to take on a greenish hue. The color can transfer to your strands and leave your hair with a ghastly green glow. The lighter your hair is, the more noticeable the green tinge will be. 
  • Your color will be unpredictable – When you expose hair dye to the air, chemical changes can affect how well your color takes. You might rinse your hair only to find that your color came out lighter or darker than expected. Your color might also come out patchy and uneven.  
A black girl that's starting to see a gray hair or two is planning to use an old hair dye to color her curls light blonde.

Can You Preserve Leftover Mixed Hair Dye?

Once you mix your hair dye with a developer, it loses its shelf life. If you don’t use all of it, you’ll have to throw away the excess after an hour. You can, however, preserve your unmixed hair dye and save it for a later date.

Just put it into an air-tight container and store it in the fridge or at room temperature, and it’ll last for about six weeks. While your color might not come out as saturated as it would have with fresh dye, it will still be safe to use. 

A black woman with medium brown natural hair, wearing semi-permanent hair color on her locks.

How to Dispose of Leftover Mixed Dye

Hair dyes contain hazardous chemicals that can be detrimental to the environment, so never put them in the recycling bin, down the drain, or with your household trash.

Harmful ingredients like paraphenylenediamine (PPD) can end up in your soil or water system and make it unusable. In addition to being harmful to humans, PPD is lethal to fish, wildlife, and vegetation. 

Instead, the best way to dispose of hair dye once it’s been mixed is to throw it away at a hazardous waste collection center. If that isn’t a convenient option where you live, you can also throw it away in a mixed waste container.

Most areas have specific rules on how to dispose of hazardous material, so research your local guidelines to find out more information. Some local municipalities offer drop-off locations that are much more accessible than a trip to your nearest hazardous waste facility.  

An African American woman with medium brown natural curls is seen sporting semi-permanent hair color on her head.

Tips to Minimize Waste When Dyeing Hair

Since you can’t save or reuse it, leftover hair dye is a waste of time and money. It’s also difficult to dispose of correctly. Want to learn how to minimize leftovers?

Keep reading for some expert tips.  

  • Only pour out what you’ll need – Preparing the right amount of dye means there won’t be much leftover when you finish. Before coloring your hair, decide how much hair color you’ll need. Unmixed hair color lasts significantly longer, so don’t mix the entire tube of dye unless you’re sure you’ll end up using it all. 
  • Share your leftovers with a friend – Another great way to minimize waste is to invite a friend to join your dyeing session. They can help you with all those hard-to-reach areas and ensure you don’t miss any spots. And if they’re game, they can use your leftover dye. If there isn’t enough dye for both of you to get all-over color, you can do some fun streaks. It’s also a cool bonding experience for you and your friends, family, or roommates.
  • Switch to natural alternatives – Switching out your harsh chemical dye for a wholesome, plant-based alternative is an easy way to cut down on leftovers. In addition to being better for your locks, you won’t have to worry about creating hazardous waste. Need some natural dye ideas? Here are some natural ways to lighten or color your hair:
    • Chamomile tea
    • Beet juice
    • Carrot juice
    • Henna
  • Use semi-permanent dye instead – Switching from permanent to semi-permanent color can help reduce waste and prevent chemical damage. Semi-permanent hair color isn’t mixed with a developer, so the risk of side effects is drastically lower. The best part? If you have leftover semi-permanent dye, just close the container and put it in the fridge. It’ll last for weeks, just in time for your next touchup.  
  • Color your hair extensions – Do you have human hair extensions lying around? You can use your excess dye to give extensions or wigs a fun pop of color. You’ll be able to cut down on waste and create a beautiful, custom hair piece. Just plan things out before you dye your hair. That way, you’ll have everything you need ready before your hour is up. 
  • Thoroughly saturate your hair with color – Having too much dye left over might signify that you didn’t use enough during your coloring process. When you dye your locks, thoroughly saturate every strand with color. Using enough dye makes it less likely that you’ll miss patches and can help ensure your color comes out deeply saturated and even. 
  • Give yourself matching brows – Got some leftover dye? Consider coloring your eyebrows to create a fun, edgy look. Keep in mind that this method only works if you use semi or demi-permanent color. Permanent hair dye is too aggressive for your delicate facial skin and can cause a bad chemical reaction. It can also drip into your eyes and lead to blindness. 
Light-skinned black woman with medium brown natural curls who is wearing semi-permanent hair color on her head.

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You might be tempted to hang onto your mixed dye to save money, but it’s not worth the risk to your hair. Luckily, you can take steps to prevent waste and keep both your hair and the environment healthy.

We hope the information we’ve gone over today has answered all of your questions about how long hair dye lasts after it has been mixed. We wish you the best of luck with your hair dye adventures!

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