soooo i had this great stylist when i was living in CO...the climate there is very very dry and i never had any dandruff issues....so i move to NY where it is more humid and suddenly dandruff. while on a biz trip to CO, i'm desperate for a good cut so i book with my old gal and tell her about the dandruff. she says to use over the counter once a week and regular the rest of the time. and then she, a native new yorker, told me that there's two kinds of dandruff, one caused by dry scalp the other by dampness. i had the dampness kind. so it is possible to have oily hair and dandruff...excess moisture can also be the problem. i was getting so upset because i thought i was falling to pieces after our move. i now use head n shoulders once a week and really massage well. i typically wash my hair every other day.
i hope this helps
