Essential oils, pure or diluted?

For some time i've been using essential oils on my scalp to fight the itching and dandruff/sebum. About 3 or 4 times a week i use tea tree, lavender, yoyoba and cod liver oil. It helps a lot, especialy the tea tree i like but the smell is bad so i only use it over night. But now i read that essential oils should always be diluted in a base oil or distilled water. Is this true?
I always use them pure, about 2 ml directly on my scalp. Would it be a good idea to mix any of these oils? I always use one at a time. What other oils would be benificial for hair?

Hi maup,

essential oils should be diluted.
Have you seen the 'Lavender, Ginger and Rosemary... '-thread?

At the moment I'm trying to work out what could be a useful oil-mix (have read a lot about / experienced
a lot with oils in the past and now I'm - nearly - convinced that the right oil-mix is able to work miracles).
What I learned so far is that sage (and burdock?) is a must. As said before I'm working on it.

Any further ideas, thoughts etc. concerning essential oils ?