The action of essential oils according to classification of their major component is simplistic and totally incorrect. Some aldehydes are common food ingredients, while others such as cinnamic aldehyde are severe skin irritants. This is a classic case of aromatherapists building a pseudo-science of convenient explanation around an incredibly complicated field in chemistry and molecular biology. Another complication in oil chemistry is that of 'isomerism' or chemicals which have different forms. Thujone does not exist as one chemical - it has isomers one of which is four times more toxic than the other.
Some oils contain a lot of one isomer and other oils a lot of the opposite isomer.
The Latin names for oils are often used incorrectly in relation to the botanical sciences. Generalisations are often made which bear little relation to the actual plants being used for the extraction of essential oils. Latin names originally thought to provide a degree of control and preciseness over the origin of essential oils have become little more than a barrier to separate the 'professional' aromatherapists from the public at large. Qualifications in aromatherapy are more or less meaningless as there are no real standards to measure against. Aromatherapy trade organisations are there to protect their own interests, not to be an independent assessor of training standards in professional aromatherapy.