I have several hubs that cover this topic. The chances of the scale, itch, redness and shedding being something other than fungus is slim to none.
The problem is it can be caused by any kind of fungus or even multiple types. Shampoos are not designed to eliminate fungus they are designed to offer relief to itching and shedding.
I would try to find the right type of fungicide. There are hundreds of types of over the counter fungicides that can be more effective than any prescription medication. If your doctor won't prescribe the proper fungicide it will be up to you to find it through trial and error.
I would Try Lotrimin Ultra cream and see if it works. When you find the one that give quick and effective relief I would not stop using it once the rash and shedding is gone. I would keep using it long after all signs and symptoms are gone.
I would also use something like Denorex Extra Strength shampoo as a body wash and shampoo. It sure makes you feel cold but I think it might be more effective than the others. It says on the bottle that it helps with psoriasis as well.
To cure it once and for all you will have to correct your autoimmune. That is the only way to eliminate the systemic internal fungus. That is what True Cures does.
I hope that helps.