I put oil on my scalp overnight last week. It was olive oil, with some coconut oil, a few drops of sesame oil and 3 drops of oregano oil. The first wash left my hair looking wet all day as it was so moist, and smelling a bit oregano-ey. The second wash got my hair back to normal, yet very soft and moisturized. I only rubbed it into my scalp not the ends, to feed the scalp.
I like the scents of oregano and of sesame so if I go around smelling like that all day, it's not a problem - at least not for me!!!