Due to the fact essential oils are up to 100 times more concentrated than the plant or source they have come from they should NOT be placed directly onto the skin. It is always advisable to suspend essential oils into water, oil or a cream. However, there are certain oils and occasions when the direct application is absolutely the best way to apply them.
If you burn yourself, are bitten by an insect or have a pimple appear, a direct application of Lavender or Tea Tree oil may be very beneficial as it is quick, easy and specific. Remember though as already mentioned, because essential oils are highly concentrated, apply them in small amounts only - one drop is often completely adequate.
When using high grade therapeutic essential oils it is the high antiseptic and antibacterial qualities that makes this method of use so viable and effective. I always have a bottle of Lavender in my hand bag and never go away without it.