Cumin oil, which is safe to use in your food, can cause blisters if you put it on your skin. Citrus oils that are safe in your food may be bad for your skin, especially if you go out into the sun. And the opposite is true, too. Eucalyptus or sage oil may soothe you if you rub it on your skin or breathe it in. But swallowing them could can cause a serious complication, like a seizure.
There are also quite a few studies that have found essential oils to be helpful for hair growth. One such study, conducted in 2015, evaluated the efficacy of rosemary oil on patients with androgenetic alopecia, or male or female pattern baldness. Patients were randomly assigned to rosemary oil or minoxidil (a medication commonly used for hair loss) for a six-month treatment period. Researchers found that both groups experienced a significant increase in hair count at the six-month endpoint. They also indicated that scalp itching was more frequent in the minoxidil group. (17)
Simple smells such as lavender, chamomile, and rosewater may help keep you calm. You can breathe in or rub diluted versions of these oils on your skin. Scientists think they work by sending chemical messages to parts of the brain that affect mood and emotion. Although these scents alone won’t take all your stress away, the aroma may help you relax.