to excess oil produced by the oil glands in your scalp. This causes the harmless bacteria that live in the scalp to proliferate and feed off the oil, which produces the odor.
Second possibility is of a fungal infection causing tinea
and hair fall also. Diagnosis is by clinical examination of the scalp as well as a skin lesion biopsy with microscopic examination. Till then , try medicated shampoos for dandruff
. There are a number of over-the-counter shampoos available that can help. The most effective ingredients -- antimicrobials -- to look for are zinc pyridinethione, selenium sulfide, sulfur and ketoconazole (also available by prescription).
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.