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How Long Can I Keep Mixed Hair Dye?

When using most hair dye, you must mix it with a developer before applying it to your hair; this becomes known as a mixed dye. But how long can you use hair dye after mixing it?

In this article, we’ll discuss why you shouldn’t use leftover hair dye after a session of dyeing your hair.


How Long Can Mixed Hair Dye Last?

Mixed semi or permanent hair dye with a developer should last at least 30 minutes and must be used within an hour after mixing.

When you apply the developer to the dye, the two substances undergo a chemical reaction, which will help the dye seep into your hair when applied.

However, once this reaction has begun, the mixture will slowly oxidize in the open air. For the first half hour, this reaction allows the dye to penetrate the cuticles of your hair. After that, the reaction subsides, and the dye will no longer be effective and possibly unsafe. So, you can consider that mixed hair dye as expired.

when does mixed hair dye expire


Can I Use Mixed Hair Dye the Next Day?

No, the chemical reaction in the mixed dye is only effective for a brief window of time. If you have leftover unmixed dye, you can store it in an airtight container in a fridge or at room temperature.

But if it’s over 30 minutes since you mixed the dye with the developer, the dye is expired and you can’t save the leftover mixed dye.

Saving unmixed dye for a later date will shorten the dye’s shelf life and likely reduce the saturation of the dye’s color.


Why Should I Avoid Preserving Mixed Hair Dye for Too Long?

Preserving mixed hair dye past its recommended use time can result in numerous undesirable side effects. An old mixed dye can be more likely to cause irritation or even an allergic reaction on your skin.

Most developers for dye use chemicals like peroxide, which is excellent for allowing the color to permeate into your hair but can be harmful over time as it oxidizes.

In addition, the usage of old mixed dye often results in undesirable colors. For example, dyes that use metallic salts in their ingredients can turn your hair green once the dye has oxidized for too long.


How To Make the Best Use of Time and Hair Dye After Mixing

How To Make the Best Use of Time and Hair Dye After Mixing

Since you only have a 30-minute window to apply your mixed dye, making the most of that 30 minutes is essential. One way to dye your hair more efficiently is not to use the hair dyeing kit and instead use a hair dye brush or your own hands, but make sure you wear gloves.

Furthermore, if you don’t need a lot of dye, you can portion only the amount you need for mixing and save the rest for another time.


While dyeing your hair at home saves time and money, it’s crucial not to be careless with your products and to know how when your mixed hair dye will expire. You’ll likely wonder how long you can keep mixed hair dye. The mixed dye can only be used for half an hour; if used after that, you will risk causing damage to your hair and skin.