What causes a scaly area on the scalp?

I'm curious if anyone knows what might cause a small scaly area of skin on the scalp?

My son has one small spot above his temple and to the right. It doesn't bother him, it's not red or sore. But if he doesn't shampoo every single day it starts to get scaly and flake. We;ve tried tea tree shampoo and medicated shampoo but it never goes away.

Is that psoriasis or something along those lines? I'm thinking no because there's no redness at all.

    Comment deleted
      In my family it's caused by dairy and chocolate. Grace has different spots around her body that get aggravated.. Other than that it's just eczema on her scalp.
      My grandpa had it his whole life, but only on the scalp.
      About Melissa
      Birth: December 31
      On Moms.com since: Mar 3, 2014
      I am a single mom of two fantastic kiddos that I love to pieces. Currently in school working towards my teaching degree. You can find me most days on www.mommathoughts.com when I am not here chit chatting! :)