and i found this....(hope it helps)
In essence, most mainstream shampoos are glamorously packaged surfactants - chemicals that dislodge dirt and grease. You will find it hard to find a shampoo that doesn't specify its suitability for "daily use" or "frequent washing" despite the fact that most dermatologists warn that over-washing hair strips it of its natural oils. The scalp secretes sebum, which naturally lubricates and protects hair against dirt and bacteria.
Left to their own devices, our own natural oils in effect wash our hair without water or extra products. In fact, hair products have been shown to over-stimulate oil glands and attract dirt.
Few of us, however, may be prepared to run the risk of social exclusion by leaving our hair unwashed. The first six weeks are said to be the worst, culminating in a very oily phase between weeks five and six. This first phase conforms to the popular perception of unwashed hair - uncomfortable and unhygienic. But after this period, non-hair washers report healthy, self-regulating hair that looks better than ever. So good, in fact, that many vow never to wash their hair again