I read somewhere that the yellowish coloring has to do with yeast overgrowth on the scalp. Maybe try some Nizoral shampoo which is an antifungal shampoo. Use it at least 3-4 times a week, leave on your scalp for approx. 5 minutes each use to allow the medicine to do its work. It usually takes several weeks to help clear the scalp. Another dietary trick that works for my family (which we found out accidentally) is to eat a gluten free diet (look up on the internet). Go figure. I don't know why the diet helps with yeast overgrowth on the scalp...though I know it helps eliminate yeast overgrowth in the intestines, but it seemed to quickly get rid of itching on the scalp and then the patches went away in a few weeks time (without Nizoral). Hope this helps.
It can be due to fungal infection or vitiligo. It is a pigmentation disorder in which melanocytes (the cells that make pigment) in the skin are destroyed. As a result, white patches appear on the skin in different parts of the body. Diagnosis can be confirmed by external examination, blood tests to check skin cell count for melanocytes and biopsy of the skin patches.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.