This may feel like In addition, switch up your shampoo to a better quality, gentler shampoo. A cleansing shampoo will be less harsh on your red hair than a lot of high street products, meaning you should feel the need to shampoo less frequently, too. Sourced from: http://gingerparrot.co.uk/2015/11/why-conditioner-is-more-important-than-shampoo-for-redheads/
There are shampoo rules that a redhead should stick to religiously. They should also know that not all shampoos are good for them.
Sourced from: https://howtobearedhead.com/4-products-that-make-red-hair-more-vibrant-without-hair-dye/
"Do a weekly deep conditioning treatment on your hair which will help keep the red pigments and luster in your hair." Sourced from: http://www.livingly.com/Daily+Dish/articles/GY4_dWGx8XI/How+Take+Care+Naturally+Red+Hair