I don’t know. Sigh. I lean toward it being more of a myth, though two days ago, I bought a shampoo and conditioner to “protect” my red.
My hair dresser tells me that the color will fade with time and there’s not much to do about that, though certain products work better at sustaining the color than others. However, she can’t tell me what those products are, because the salon she works at doesn’t sell them.
Therefore, we’ll meet for drinks and I’ll “drunk” it out of her.
But seriously, if the shampoo costs the same amount as normal shampoo, at least it’s not a waste of money. Just don’t expect miracles. The ingredients on these products don’t differ much from ingredients on other shampoos, except for dye that is added to make the shampoo more marketable.
What you do need to be careful about is using one on your hair if it’s not colored, or it’s vastly different from your color. I learned this the wrong way, when I was a platinum visiting my mother who had her hair dyed red at the time. I grabbed her shampoo by mistake, and spent three days with a huge pinkish spot on the side of my head. But even then, that mistake faded pretty fast.
Because of that, it seems like these shampoos might work at giving the color a temporary boost and enhancing the shine of hair to some degree, but they don’t really make the color last longer.
To preserve color, wash your hair less—skip non-workout days— and avoid harsh ingredients which will strip color.