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 after it’s 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?
You can’t keep mixed hair dye for later. Once you mix your hair dye with a developer, use it right away, within the time the box directions give, and throw out whatever’s left. Never cap a bottle of mixed dye or seal the leftovers in a container, since the mixture keeps releasing oxygen and the pressure can build until the container bursts. 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. On its own, bottled developer is fairly stable. Once it’s mixed with the dye, though, the reaction starts right away and keeps going in the bowl.
The peroxide slowly breaks down into water and oxygen, and the color keeps forming in the bowl, so a mixture that sits around gets weaker and less predictable. Read this article to learn more about the dangers of using expired hair dye.
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Why You Shouldn't Leave Mixed Dye Out Too Long
Leaving your dye out for a while may seem harmless, but the reaction that keeps going in the bowl will throw off your results. Here are some risks of leaving mixed hair dye sitting out.
- Skin irritation and burns - Your skin can react to hair dye whether it’s fresh or has been sitting out. Lab studies suggest some of the compounds that form as dye sits are strong allergens, but that hasn’t been tested in people, so the safe move is the same either way. The FDA says to do a skin test before every use: dab a little on the bend of your elbow and wait 48 hours. Wear gloves when you apply color, too. An allergic reaction 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 or irritation are:
- Paraphenylenediamine (PPD), the most common hair dye allergen
- Ammonia, which can irritate your skin
- Hydrogen peroxide, which can also irritate your skin
- Resorcinol
- 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 or irritation are:
- Your dye can turn green - Old dye can give you a shade you didn’t pick, but a green tinge usually has another cause. It tends to come from blue or ash pigments landing on yellow tones in your hair, or from copper in pool or tap water building up on light or damaged hair, and either one can 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 - Once it’s mixed, the color molecules keep forming in the bowl, and the bigger they get, the harder it is for them to get into your strands. You might rinse your hair only to find that your color came out lighter than expected. Your color might also come out patchy and uneven.
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, throw away the excess as soon as you’ve finished applying. You can, however, preserve your unmixed hair dye and save it for a later date.
Just leave each part in its original tube or bottle, cap it tightly, and keep it somewhere cool and dark at room temperature. If the box has a date or an open-jar symbol, follow it. If not, use an opened tube within about six weeks. Your color might not come out as saturated as it would have with fresh dye, and you’ll still want to do a skin test before you use it.
How to Dispose of Leftover Mixed Dye
Hair dyes contain hazardous chemicals that can be detrimental to the environment, so don’t pour leftover mixed dye down the drain or put it in the recycling bin.
Harmful ingredients like paraphenylenediamine (PPD) can end up in your water system, and PPD is very toxic to fish and other aquatic life.
Instead, check the box for disposal directions first. The EPA lists hair dyes as household hazardous waste, so a hazardous waste collection center is the best place for leftover mixed dye. If that isn’t a convenient option where you live, federal law allows it in your household trash, so check your local rules. Either way, don’t cap it or seal it in a bag or bottle first.
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.
Tips to Minimize Waste When Dyeing Hair
Since you can’t save or reuse it, leftover mixed 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. If your kit is made to be mixed all at once in its applicator bottle, follow the box, since the ratio matters.
- 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. Just make sure they do their own skin test 48 hours ahead, since mixed dye has to go on right away. 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. You may also have less hazardous waste to dispose of, but read the label, since some products sold as plant-based, and anything sold as “black henna,” can contain PPD. Need some natural dye ideas? Here are some natural ways to tint or color your hair:
- Chamomile tea, which can add a yellow tint to light hair
- 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 it’s gentler on your strands, although you can still be allergic to it, so do a skin test first. The best part? If you have leftover semi-permanent dye, just close the container tightly and store it the way the label says. If there’s no date, use it within about six weeks, just in time for your next touch-up.
- 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 ready before you mix your color.
- 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.
- Keep it off your brows and lashes - Got some leftover dye? Don’t use it on your eyebrows or eyelashes, even if it’s semi-permanent. The FDA says no hair dye is approved for brows or lashes, and dye near your eyes can hurt them and may even cause blindness.
Related Articles
- Can Henna Expire?
- How to Read Expiration Dates on Hair Products
- Does Powder Hair Bleach Expire?
- Can You Reuse Hair Dye After Opening It?
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!
