Hello and welcome to healthcaremagic Chronic dandruff, specially when it is in the form of well defined, scaly plaques of erythema could be due to psoriasis. Scalp psoriasis may be associated with patches elsewhere on the body. A thorough cutaneous examination may reveal patches at other sites, thus confirming the psoriatic nature of the patches on scalp. Scalp psoriasis may also occur in isolation without involvement of any of the rest of the body. If I was the treating doctor I would suggest you to wash your scalp at least thrice weekly with coal tar+salicylic acid based shampoo(Protar shampoo OR Ionax-T shampoo). Psoriasis is a steroid responsive dermatosis and therefore a topical steroid + salicylic acid based lotion, twice daily for 2 weeks, would help in loosening up the scales as well as resolve psoriatic lesions. However, steroids are not advisable for regular use therefore I would suggest that once the patches show remarkable improvement with topical steroid lotions you may use a topical Vitamin D analogue e.g calcipotriol lotion, twice daily for the disease that is left over. Psoriasis is a chronic disease which can relapse, therefore it is advisable to use a coal tar based shampoo regularly (once or twice weekly) for maintenance to prolong the remissions. Hope this helps Regards