Good Sulfate Free Dandruff shampoo

I have only every had the basic head and shoulder's shampoo work for. Every other shampoo seems to work for a week or 2 and then just stops working. My dandruff unfortunately gets to the point the skin around my eyebrows and nose start to scab and dry up (and my beard a bit). Recently I got a keratin treatment and I wanted to know if there was a good sulfate free dandruff shampoo (keratin treatment requires sulfate free shampoo to maintain the straight hair). I have the Harry's shampoo but I feel like it didn't fully work.