Talk to Dermatologist on Persistent Dandruff On Scalp And Beard

Hello Everyone I have been experiencing persistent dandruff on my scalp and beard for the past 5–6 weeks. Fine white flakes develop again by the very next day after washing. There is no itching, and the skin becomes red and occasionally bleeds slightly only when I scratch off the flakes with my fingernails. I have been using HYSEKE Ketoconazole 2% Hair Solution, which provides significant relief, but the dandruff returns if I miss even one day. I am also diabetic. I am sharing pictures of the affected areas and the shampoo I am using. Could you please advise me on the likely cause, the appropriate treatment, and how frequently I should use this shampoo for long-term control? Thank you,