Hi, As you said your father suffers from psoriasis from last 20 years.. I would like to say few things about psoriasis. Psoriasis is a chronic relapsing and autoimmune disease. You may be having scaly plaques on various parts of the body,scaly lesions on the scalp. Exact cause is not known. Genetic tendency, autoimmunitity, stress,dry wheather...etc may be responsible for precipitation and exacerbation of psoriasis. You consult dermatologist for firm diagnosis and treatment. I usually recommend cap acitretin 10 mg twice a day along with methotraxate 15 mg weekly in three devided doses 12 hourly...for psoriasis.This may be taken for long time till good response. Blood tests may be done to monitor the treatment. For itching, you may take antihistamnics like levocetirizine. Avoid oral stetoid,as it may lead to flare up of the lesions. Tell him to apply mild steroid cream or calcipotriol oint on the lesions on the psoriatic lesions. He may apply moisturiser to improve the skin texture. He should avoid soap bath for few weeks..And he should be free of stress and worries as that might worsen psoriasis. He might get good result.I hope you got my answer. Thanks. Dr. Ilyas Patel MD