Hair dye products don’t typically have expiration dates on their package. This can cause confusion for consumers who are wondering if old hair dye still works and is safe to use.

According to manufacturers, unopened hair dye doesn’t expire. They caution, however, that hair dye has a shelf life of about 3 years.

After that period of time, hair dye may not work effectively. There’s no evidence that old hair dye is dangerous to use. However, old hair dye that contains chemicals may cause unwanted side effects to your hair or scalp.

Read on to learn more about hair dye that may be past its prime — and if you should use it or lose it.

When dealing with hair dye that may be expired, the first thing to consider is if the container is open.

Once opened, any type of hair dye may become contaminated by bacteria or fungi. If this occurs, a bad smell may result. This should be your warning to toss it. Opened hair dye is only safe to use for a limited window of time.

Here are some of the other things to watch out for if you have hair dye that’s potentially expired.

Something is wrong with the package or chemicals

Unopened hair dye may appear perfectly fine to the eye (and nose). However, there are signs that may indicate that it’s gone bad.

These include:

  • a sour, strong, or unusual smell that differs from the ammonia scent associated with hair dye
  • unusual color
  • liquid that’s streaked or separated
  • cracked bottle
  • leaking bottle
  • caking around the bottle cap
  • damaged or dented packaging
  • packaging that’s faded

Containers have been open for too long

Most forms of hair dye come packaged with two separate product bottles or pouches that need to be mixed together. If you’ve opened the containers but not mixed the ingredients, they may start to oxidize, even if stored correctly.

Oxidation is a chemical reaction which can adversely affect the chemicals in hair dye. Any opened product that has been exposed to sunlight, air, moisture, heat, or humidity will degrade and oxidize more quickly.

Manufacturers typically recommend using opened, unmixed containers within 6 weeks. After that time, if oxidation has occurred, you may get a darker color result when you dye your hair.

Natural products that don’t contain chemicals or preservatives will also degrade rapidly after they’re opened, no matter how they’re stored.

Warning

Mixed hair dye must be used within 1 hour. Mixed hair dye is dangerous to store, has no shelf life, and can’t be used at a later date.

Healthline

Old hair dye hasn’t been shown to damage either the hair follicle or hair shaft. It likely won’t change the texture of your hair or cause it to fall out or break off.

The most likely effect of using old hair dye is that it won’t work or that your hair will be a darker shade than you were anticipating. In some instances, you may get uneven color results.

There are, however, some other negative effects that using expired hair dye could potentially have:

Greenish discoloration

While some people claim anecdotally that old hair dye will turn your hair green, there’s no scientific evidence that supports this.

However, if you have light blonde, white, or gray hair, it may take on a green tinge. This is the result of oxidation on hard metals, such as copper, that are used in hair dye.

Allergic reactions and burns

Permanent hair dye causes chemical changes in the hair and is the type most associated with health risks like burns and allergic reactions. But some people will always experience symptoms caused by hair dye, whether it’s new or old.

Some of the chemicals in hair dye that may cause allergic reactions include:

  • paraphenylenediamine (PPD)
  • resorcinol
  • ammonia
  • hydrogen peroxide

The oxidation that comes with age may exacerbate the effect of these chemicals.

Allergy symptoms

Symptoms of an allergy to hair dye may appear up to 72 hours after application. These include:

  • burning
  • redness
  • hives
  • sores
  • itching
  • swelling of the face
  • trouble breathing, or other symptoms of anaphylaxis

If you’re sensitive to hair dye that contains chemicals or are allergic to any of its ingredients, don’t use it.

Healthline

If you wish to avoid chemicals, you can use organic, henna, or natural hair coloring products.

You can also use ingredients you may already have in your kitchen. Juices and homemade elixirs are most effective on light-colored hair.

Things you can use to try dyeing your hair at home include:

  • lemon juice
  • chamomile tea
  • carrot juice
  • beet juice
  • coffee

Hair dye boxes typically don’t have expiration dates. However, most manufacturers indicate that hair dye has a shelf life of about 3 years.

The most common result of using old hair dye is that your hair won’t change color. In some instances, you may get uneven coloring results or a green tinge.

Hair dye that contains chemicals may cause allergic reactions and other health risks. These reactions may be intensified by the product’s age.