Aromatherapy is more than something that smells nice. We all know that Lavender is used to treat burns, but did you know that Anise is a Neural Toxin and can cause epileptic seizure if given at the wrong dose? Let's take a look at Rosemary (be warned I am going to give you an overload of aromatherapy here). It is used for skin & scalp care, it stimulates the nervous system, is an excellent antiseptic and discourages the build-up of acids in the joints.
Principal chemical constituents: There are four main CTs of Rosemary, although up to 8 are known to exist. CTs include Rosemary that is high in Camphor, a-Pinene, 1,8-Cineol, Borneol, and Bornyl acetate. Mainly, the following components are found. Pinene, Camphene, Cineol, Camphor, Borneol, and Sesquiterpenes. B-Caryophyllene are found in rosemary (linalool type). Rosemary Cineol: Main components: cineole, terpene hydrocarbons. Rosemary Verbenone: Main components: ketones (verbenone), cineole, terpene hydrocarbons). Rosemary CT Camphor: Main components: terpene ketone (camphor), terpene oxide (cineol), terpene hydrocarbons.
Characteristics – color/odor: The colour of this oil is pale yellow. The scent is slightly camphoraceous and fresh.
Therapeutic uses: This oil may be beneficial for skin conditions and dandruff. Rosemary restores hair loss and colour. (Note: This is not proven or claimed, possibly just an old wives tale).
Rosemary induces a positive state of mind and emotions. Its aromatic influence stimulates memory and opens the conscious mind because it is an excellent brain stimulant. This oil aids concentration, indecision, procrastination. This oil stimulates and unblocks various systems in the body.
In France it was traditionally used to fumigate sick rooms and hospitals. The practice of burning Rosemary in hospital wards persisted into the present century.
Rosemary oil discourages the build-up of acids in the joints that lead to arthritis.
Rosemary will help itchy skin, dry or sluggish skin and coat on animals (not cats) and helps fight against skin parasites as well.
Rosemary CT Camphor: Neuromuscular action that is variable depending on dose. It helps in the production of bile.
Rosemary CT Cineole: Good for bronchial-pulmonary infections.
Rosemary CT Verbenone: It is especially effective as the beginning mucolytic treatment of bronchial and cold conditions such as chest, lung, infections. An aromatherapy classic, this oil’s regenerating qualities and the way it is tolerated by the skin make it essential for skin care.
Therapeutic properties: Rosemary CT Cineol: Antibacterial especially on staph or strep germs including Eschericia coli.
Rosemary CT Verbenone: Mucolytic.
Rosemary CT Camphor: Neuromuscular
Precautions: Rosemary needs to be emphasised that in normal aromatherapy dosages, there is very little, if any, risk of negative effects with any of the chemotypes.
Rosemary CT Camphor: Rosemary CT Camphor contains oxides and can negate the effects of anesthetic. It is a nonhormonal emmenogogue. Contains ketone; not to be used by children less than 10 years old or pregnant women.
Rosemary CT Cineole: Epileptics should use with caution. If pregnant or under a doctor’s care, consult physician.
Rosemary CT Verbenone: Verbenone is considered an unknown ketone content. Epileptics should use with caution. If pregnant or under a doctor’s care, consult physician. Children less than 10 years old and pregnant women should use with caution.
Extra eucalyptol is often added to rosemary, as well as terpenes from cypress, camphor, eucalyptus, sage and synthetic terpineol.
This goes through the most basic information on Rosemary. I hope that helps to understand the basic therapeutic properties of rosemary.
All essential oils have miniscule particles that are able to bypass the blood brain barrier as well as the placental barrier which is why it is often recommended to avoid using while pregnant because it may not be the mother that is harmed (although with Rosemary because it is an emmenogogue can cause a miscarriage - emmenogogue means to bring on your period or cause the menstrual blood to flow) but it is going directly to the baby whose immune system is simply ready to withstand essential oils.
At 3% as a general guideline we know that people who have a compromised immune system, seniors, children and alcoholics it is therapeutic. For the average healthy person 5% is fully therapeutic and is the general guideline but each essential oil is different. If you were to go into the aromatherapy section here you would find pinned the banned and restricted essential oils which will talk about the limitations of use or percentage, of the extremely dangerous essential oils.
Most babies should not be exposed to any essential oils until they are at least 6 months old, not even an oil burner in their room because, again, their immune system is simply not ready, and this includes lavender.
Sorry this is such a long post, but I want to help you understand how essential oils are used and why we say that 3% is generally accepted as safe. It is far better to study each oil that you want to use so you understand the restrictions and contra-indicators.
This is only part of the information I have on it from my training.
I'm not sure I "explained" anything other than my confusion, but thanks for your generosity. 
