The effect on your nails isn't going to be helped with a topical, this symptom is from a systemic issue. Not everyone with psoriasis gets the hair and nail symptoms. Diet might help, you can also try a hair and nail supplement. The itchy skin is different for everyone. While a cortisone cream can be helpful, there are so many other factors that effect psoriasis because it is an autoimmune disorder. For me cortisones only helps if I catch it right away, the biggest help is my diet, stress and skincare routine. This took me years to figure out and I am still learning new things. You could try elimination diets to dial in if your nutrition is a factor. Make sure you do your homework with this, you can effect your vitamin, mineral and electrolyte balance when you do this so being educated is crucial so you don't add a bunch more issues. If you have a holistic health store near you, they usually have someone who is very experienced that can help you navigate this. Some doctors want to start throwing medications at the problem right away, and though medications are necessary for some people, some can be controlled without. The medications that are prescribed for psoriasis usually entail stifling your immune system. Sorry so long winded.