Any of the essential oils classified as stimulant or cephalic can help to reduce mental fatigue, though it would be very unwise to over-use any of them. You might sensibly use one of them to tide you over a crisis, or some short period of time when you really need to think clearly in spite of being tired, but in the long run, it really is better to take adequate rest and breaks from mentally demanding work.

Basil, Peppermint and Rosemary are the oils most often used for this purpose, and of these Rosemary is the most helpful, though others may prefer Basil. A bath with 6 drops of Rosemary is wonderful if you have woken exhausted in the morning and know that you face another tough day. Peppermint is best used in the form of peppermint tea, which is far safer than using strong tea or coffee to help you through a long stint of work.

One good way of keeping yourself alert and clear­headed is to put 12 drops of Rosemary oil in an essential oil burner on your desk. In circumstances where this is not possible, such as when driving on a long journey, you could put a single drop of Rosemary on each wrist, so that as you move your hands the vapour will be released for you to inhale. You can also do this do this when writing.