Turns out washing your head with shampoo twice and blow drying afterwards fixes my itchy scalp. Don’t ask me why, I don’t know. I just know that since my hairdresser did that, I feel so much better.
Thought I’d spread the word, because it is so frustratingly simple :D
Out of curiosity, do you have super thick hair and only towel dry it after getting out of the shower? Reoccurring dandruff means you have a fungal infection, and they tend to prefer warm damp environments. Blow drying may prevent it, because thick hair tends to trap moisture and take a while to dry. Which allows the fungus to multiply in the meantime.
I have thick hair, but not as many as I used to. Still, good point I could blow dry it.
So now I need to find a silent / bearable hair dryer.