Hi and thank you for your question. I am a verified Expert and I am happy to help you today.
I can imagine this must be very annoying to you... not to mention the potential for a secondary infection due to scratching. The application of Nizoral shampoo may not be enough... ( if it is even fungal) I would recommend you ask your Doctor to culture a scraping to see what it is, which will dictate the best modality of treatment. Simple answer, but I think this is the way to go on this.