Prolonged use brings a risk of burning of the mucous membranes, and possible upset of gut flora. Overconsumption can cause possible liver or kidney toxicity.
The most common uses are Direct inhalation (diffusers, heat, spritzers, steaming, baths); Secondary inhalation (cleaning products, air fresheners); and Topical application (salves, compresses or with massage).
If you are taking homeopathic remedies do not use black pepper, camphor, eucalyptus, peppermint, rosemary, or spearmint.
There are many good quality supplements for general health as well as to help control and prevent specific diseases.
Hydrosols are usually used by spraying for things like air fresheners, deodorant or body spray .