Not rinsing after shampoo: will it make things worse?

[vauxall]

I have been using Nizoral and more recently the Ginger Shampoo with Piroctone Olamine. I have started not to rinse my hair completely after washing, in order to leave a bit of the active component on my scalp. I wash my hair every other day so the thingy would stay on my scalp for 48 hours. Am I making things worse? I feel my scalp a bit itchy and it kinda gives me a little headache. Your opinions!