Boyfriend has bad dandruff

Au

My boyfriend has really bad dandruff. He will lean on the car rest and it will be covered in flakes and so will his pillow.

He doesn't wear black shirts because of this too.

When I run my hands through his hair, all I do is stir it up and make it worse, so I can't even rub my man's head.

I've bought him Head & Shoulders and he's used it but it hasn't worked much.

What do you recommend, ladies?