Hello. Thanks for writing to us at healthcaremagic Dandruff if excessive or resistant to treatment with regular OTC shampoos can be due to either seborrheic dermatitis or scalp psoriasis. While seborrheic dermatitis is associated with faintly red patches, itching and yellow greasy adherent scales; psoriasis is characterized by well defined deeply red patches, with thick candle wax like scales. The diagnosis of psoriasis is clinical in most cases. There may psoriatic plaques elsewhere on the body as well. If I was the treating doctor I would have asked you to use a coal tar+salicylic acid based shampoo, daily or every alternate days for mild psoriasis affecting the scalp. Depending on the clinical severity of psoriasis, dermatologists may also ask to apply a topical steroid+salicylic acid lotion for 2-4 weeks, if there are thick scaly plaques of psoriasis, as shampoo alone might not be sufficient. Other effective options apart from steroids that are available to treat scalp psoriasis are topical Vit D analogues like calcipotriol and calcitriol. Psoriasis can recur again after seemingly complete cure. Therefore, once the patches and scaling is effectively controlled with topical treatment with lotions, a shampoo would be effective for maintaining the improvement. These are all prescription products, therefore, I would suggest you that you talk to your dermatologist for the needful. Your dermatologist would be able to assess whether shampoo alone would be effective or do you require additional topical treatment with lotions. Regards