I have never used for that but I'll just put what it says in the book (kinda long) :
Acne results from an excess accumulation of dirt and sebum around the hair follicle and the pores of the skin. This accumulation may be due to an over-production of sebum, an oily substance that is secreted by the sebaceous glands in the hair follicles. This leads to inflammation and infection around the hair follicle and the formation of a pimple or blackhead.
Acne in adults can be caused by hormone imbalances as well as the use of chlorinated compounds, endocrine system inbalances, or poor dietary practices. Heavy or greasy makeup can also contribute to acne. Stress may also play a role.
Essential oils are outstanding for treating acne because of their ability to dissolve sebum, kill bacteria, and preserve the acid mantle of the skin. Because essential oils may be slightly drying to the skin when applied undiluted, it may be necessary to dilute them with an oil (vegetable or grapeseed) to keep the skin hydrated. Sorry so long.