Photosensitizing oils such as bergamot oil, lemon essential oil, lime essential oil, and cumin essential oil may cause you to burn in the sunlight. Yikes! Side effects vary in severity, but depending on how bad the burn is, you may experience reactions ranging from mild skin discoloration to severe burns.
Skin irritation 2
Some oils such as peppermint oil, lemongrass essential oil, cinnamon leaf essential oil, and citronella essential oil can really irritate your skin and eyes, when applied directly to your skin. Be sure to dilute theses oils (and, really, all oils) before applying them to your biggest organ--your skin.
Worsen existing condition 3
Horseradish is sometimes used to treat coughs, however the horseradish oil contains allyl isothiocyanate, which is an irritant to the skin, eyes, nose and mucus membranes. Honestly, is all of that worth getting rid of a little tickle in your throat?
Serious illness 5
Calamus root is sometimes used to treat headaches, stress disorders and vertigo. However, because the oil contains an carcinogenic called asorone, it may actually cause a lot more harm than good. Oral ingestion of this oil may lead to liver and kidney damage. Stick with aspirin if you have a headache or, better yet, just go see your doctor.
Wormwood, often found in the drink absinthe, may produce auditory and visual hallucinations. Talk about scary!
Often used as an insect repellent, tansy oil is high in thujone, which is poisonous and may cause convulsions, vomiting, uterine bleeding and DEATH! Omg, just get a fly swatter instead.