Essential Oils are highly concentrated chemicals with complex structures. They are powerful, so care must be used when working with them.
Unless you are certified in aromatherapy, essential oils should be used externally only due to many being toxic if ingested.
The following oils should only be used in moderation and for short periods at a time:
Basil, Bay, Camphor, Juniper, Cedarwood, Cinnamon, Eucalyptus, Coriander, Fennel, Ginger, Hyssop, Black Pepper, Nutmeg, Thyme, Valerian, Tuberose
A few oils are phototoxic which means they can cause senstivity to sunlight. Be cautious with them on the skin if you are exposed to sunlight frequently.
They are listed below:
Angelica, Bergamot, Citronella, Ginger, Lemon, Lime, Mandarin, Orange, Lemon Verbena
Angelica, Basil, Birch, Cedarwood, Citronella, Clary Sage, Cypress, Fennel, Geranium, Hyssop, Jasmine, Juniper, Marjoram, Myrrh, Nutmeg, Peppermint, Rosemary, Thyme, Tarragon, Yarrow
Although most essential oils can irritate the skin when undiluted, these oils are particularly irritating. Make sure to dilute them very well before using on the skin:
Angelica, Black Pepper, Cinnamon, Clove, Ginger, Lemon, Lemongrass, Lemon Verbena, Nutmeg, Orange, Peppermint