I thought I'd give salt water a try tonight. I have vague memories of my hair not looking totally greasy after a day swimming at the beach, so I took some of my pickling salt ("made with just salt" according to the box) and mixed it with some water and gave it a shot. I used probably between 1 and 2 tbsp mixed with about a cup of water. I stirred until it was mostly dissolved, then rubbed it into wet hair very well.
-it's easy to tell when it's rinsed out - the water doesn't taste salty anymore.
-there's no way I'm allergic to this... and the only other thing I used tonight was Ivory soap.
-it's dirt cheap.
-my hair didn't really FEEL degreased in the shower. However, I also skipped my normal face cleanser and my face feels nice and soft and not oily.. so maybe there's a chance that it'll work. I'll have to see tomorrow when my hair is dry.