I've been looking for a sulphate-free shampoo as I understand this is what I need to get to prevent my red hair colour from washing out in super-quick time. I was delighted to discover my favourite brand has a sulphate free shampoo, and I use the conditioner from that line - it's amazing (note, I don't actually need to straighten my hair, I just like the brand/smell/price).

However, on reading the description, it says this: note: the shampoo product utilises a blend of sulphate-free surfactants but is not sodium chloride free.

Why is sodium chloride free important? And am I likely to have a good or bad time with the above shampoo please? I've seen people rave about Aveda shampoos for red hair, but they're a bit above my price bracket at the moment.

Otherwise, I know I should only try to wash it a few times a week, and in as cold water as I can possibly handle.

Many thanks.