Ideally you got a hair dresser who knows his trade. Ask them what they suggest when you get your next hair cut. They gladly sell you some. It’s expensive (like 30-50€ a bottle) but you use only small amounts and it lasts for approx 2-3 months.

For me it stopped hair loss, itchy scalp and scales. It was a nightmare. Now, normal fat free hair. Wash every 2-3 days.