Essential oils aren’t oils at all; they are a herbal constituent containing volatile compounds that carry smell. Essential oils are often very strong in odour as they are very concentrated, they are all antimicrobial and antibacterial to some degree. If you smell anything from a plant it is an essential oil.
Essential oils are generally extracted by distillation, often by using steam. Other processes include expression or solvent extraction. The purest essential oil comes from the first extraction and it’s that part that is processed into essential oils for therapeutic and edible use. The second, third and fourth extractions contain less essential oils and often contain the solvent that has been used to extract the last remaining essential oil from a batch. These are used in perfumery, incense and cleaning products.
There is a long history of medicinal uses of essential oils, especially in Europe. The earliest recorded mention of the techniques and methods used to produce essential oils is believed to be that of Ibn al-Baitar (1188–1248), an Andalusian physician, pharmacist and chemist.
Are they herbal?
Essential oils are herbal and in law they fall under both cosmetic and herbal law depending on how they are used. The plants used and the resulting essential oils have medicinal properties, regardless of whether the essential oil is going to be used in a household cleaning product.