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Why does red hair dye fade so much?

Eire asks…I’ve been dying my hair red for a couple years and it lasts now because ive been doing it so long. The thing is red dye always has a hard time lasting. I hear this is because the molecule size is too large , BUT I think that’s only regarding the size of the molecules on natural red hair and not dyed hair. With nano technology and improved dye colors and cosmetic formulas why haven’t we found a way to remedy this problem in red hair dye?

The Beauty Brains respond:

Red has always been a difficult color to form, especially in permanent hair color.  There are basically three reasons why this is the case:

Fewer choices due to safety concerns

The  intermediates (the tiny colorless molecules which penetrate inside the hair and then react to form larger, colored polymers) always seem to be in trouble for safety reasons. That means there are fewer chemicals available for chemists to use.

More easily broken down

The polymers which create the red shades are more easily broken down by UV radiation and other forms of oxidation. Once they’re oxidized their color shifts and they’re more easily removed from the hair.

Size matters

You’re right that in the case of hair dye the size of the molecule is important. But it’s not that the red molecules are too big, rather the problem is they are too small! These red polymers tend to be of smaller molecular size and are therefore more easily removed by water, especially when surfactants are involved (i.e., shampoo formulations).

The Beauty Brains bottom line

You’re right that red is by far the toughest hair color to get and keep. Unfortunately, due to safety concerns, there’s not very much innovation in this area so don’t look for a solution any time soon.

Comments on this entry are closed.

  • rozy April 1, 2014, 4:25 am

    Which is the easiest colour? Black?

  • Colleen April 3, 2014, 10:24 am

    My colorists uses the Chromatics line from Redken and my color lasts amazingly well – much longer without fading than any red I’ve ever used. I’ve been dying my hair off and on for about 20 years.

  • carriep April 30, 2014, 9:26 pm

    I use henna & it works great. It is a bit of a production, i won’t lie, but the color is amazing.

  • Donovan October 9, 2015, 2:26 pm

    henna is very bad for your hair. I suggest getting a red color depositing shampoo and conditioner or getting it toned between appointments

  • D November 19, 2015, 11:51 am

    Henna works well but you MUST ONLY use henna on virgin (hair that contains no previous color) hair. If you put henna on hair that has already been colored it will turn it green.

  • Vica July 21, 2017, 4:29 am

    Henna is not bad for your hair, henna is actually very good for your hair. It nourishes it.

  • Lia November 13, 2017, 11:22 pm

    Who is writing these articles? What scientist?