Best shampoo/treatment to thicken hair

[LifeInAHamsterWheel]

My mum is struggling with thinning hair and I'm thinking of getting her a really nice shampoo as part of her Christmas box. Can anyone recommend something really good to help thicken the hair? Don't know if she needs a shampoo or a weekly treatment etc. but open to suggestions.

The shampoos I tried had a very drying effect on my already dry hair, so I can't help you with that, but can I suggest it would be worth your mother trying a vitamin D supplement and also collagen?

I suppose the causes vary but there's a big difference in my hair now. It took a long time, but worth a try.