How Long Does Permanent Hair Dye Last?

Formulate user Deepti has a hair dye question:

"I dye my hair regularly and it fades so quickly. I'm confused, because if it's permanent, doesn't that mean that it shouldn't fade? How long does permanent hair generally last? I want to know if mine fades more quickly. And if my hair color fades too fast, how can I prolong my hair color? And while I have you, what unnatural hair colors last the longest?

Thanks for writing, Deepti! We'll answer your questions one by one.

How long does permanent hair dye generally last?

Permanent hair dye typically lasts for between four to eight weeks before it grows out or fades (more on that below). That timeline is broad because it depends on a lot of different factors - how fast your hair grows, the amount of contrast between the color that you dyed your hair and the color it is naturally, the method that your stylist used, how damaged your hair was pre-dyeing, et cetera.

To illustrate: someone who gets a balayage, a style in which the dyed color is integrated smoothly into the hair's natural color, will be able to wait longer than someone who dyes their naturally light blonde hair raven black from root to tip. The person with the balayage will be able to grow their hair out easily - balayages subtly transition from your ends to your roots, so there's no clear demarcation of color. Our balayage friend would be able to go weeks and weeks between appointments, since their roots look natural. Meanwhile, our blonde to black friend would need to get a touch up the instant their roots start showing, since there's such a strong contrast between blonde and black. Depending on how fast their hair grows/their comfortability doing touch-ups at home, they might have to be back in the stylist's chair in under four weeks.

Does permanent hair dye fade?

Permanent hair dye is interesting, because while it is indeed permanent (you'll never be able to remove it completely from your hair without bleach), it does change color and morph over time. Permanent hair dye lasts until it grows out, but it might not always keep the exact same color. The color that it fades to and how quickly it fades depends on multiple factors, including:

The hardness of your water (if you have hard water, there will be tiny amounts of minerals deposited on your hair every time you wash, gradually changing its color)
If you bleached your hair before you dyed it (and if you did bleach, how intensely you bleached - this matters because bleach neutralizes the pigments that were already in your hair)
The color you dyed your hair (some colors fade faster than others, depending on the size of the pigment particle)
How damaged your hair was before you dyed it (if your hair is damaged it's easier for the pigment to fall out through the hair cuticle)
How much damage your hair sustained from being dyed
The color your hair was before it was dyed (did you bleach out the other pigments? If you didn't, they might show through over time)
If you heat style (causes extra damage to the hair follicle, making it easier for pigment to fall from the hair)
How often you wash your hair and if you use a color safe shampoo (every time you wash your hair you risk fading your hair just a smidge. Gentler shampoos fade colors more slowly than a shampoo that contains sulfates)
How much sun your hair is exposed to (the sun interacts with colors - if you've ever seen a yellowed, aged piece of paper, you know how this works!)
If you use a pigment depositing shampoo/conditioner (puts a little more of the original color back in your hair or a pigment that tones your hair to make it resemble what it looked like when freshly dyed)...

The list goes on and on. Because there are so many things that can influence the rate at which hair color fades (and the exact color that it fades to), it's challenging to predict exactly how long a dye job will last before a retouch is needed. Of course, that's assuming that the person actually wants a retouch - it could be that they love the color that their hair faded to (this really does happen! Faded colors can look pretty cool) and don't mind having obviously grown out roots.

"My hair color fades too fast, how can I prolong my hair color?"

If you want your hair color to fade more slowly, here are some best practices:

Wash your hair infrequently - aim for once a week. This may be challenging to transition to, but it's absolutely doable. If your hair feels extra oily days before your wash, wear your hair up with a headband. You can also use tinted dry shampoos to both soak up some oil and accentuate your color. It'll also help if you reduce the amount of styling products you use, as these can make hair feel icky and in need of a wash faster.
Check to see if you have hard water. If your shower or bathtub constantly suffers from mineral build-up or an unusual amount of soap scum, you might have hard water. You can prevent the minerals in hard water from building up in your hair by investing in a shower head water softener. Be sure to remember to change its filter on schedule!
Keep your hair out of the sun. In the winter, this means beanies, and in the summer, it means baseball caps and wide brimmed hats.
Avoid activities that further damage your hair cuticle. This means reducing heat styling as much as possible (This certainly doesn't mean that you should switch to vigorous towel drying though - hello, air drying/gently holding hair with an absorbent fabric), cutting down the frequency that your hair is submerged in water (if you love swimming in the summer, maybe plan to rock some faded hair colors), and brushing hair when wet. Most importantly, don't further chemically process your hair. No bleach, no relaxants, no brazilian blowouts.
Dye your hair with a color that's close(ish) to your natural color. The fading will be subtle - you'll be able to have the thrill of changing your hair color without having to deal with a huge amount of fading.

And what unnatural hair color lasts the longest?

Green and red fashion colors can last the longest. Second in line are any dark colors. Pastels fade very quickly. Broadly speaking, darker colors of hair dye last longer. However, the amount of time that a color stays largely depends on the brand of hair dye that you use. Some of the best brands of hair dye in unnatural colors that last long are Punky Color, Manic Panic and Arctic Fox.