ESSENTIAL OILS

Essential oils are complex mixtures of volatile organic compounds of botanical origin. Essential oils can be extracted from various parts of plants (leaves, stems, fruits, flowers, and roots). They are called “essential” oils because they reflect the inner nature or essence of the plant from which they are extracted.

At room temperature, they are liquid, rarely colored, but turn a dark yellowish color upon oxidation. They are poorly soluble in water, but are soluble in alcohols, lipids, and common organic solvents.

Their complex composition is due to the presence of many individual substances with highly variable concentrations. There are more than 200 components in pure essential oils. In general, all essential oils have 2 or 3 main components with a concentration between 20-70% and these components determine the biological properties of the oils. The components can be broadly classified as volatile and non-volatile fractions. 1-10% of the mass of the essential oil is represented by carotenoids, fatty acids, flavonoids and waxes, which are classified as non-volatile substances.

Use in cosmetics

Essential oils have a wide variety of uses in perfumery and industrial cosmetic products, due to their characteristic properties of the aromatic plants from which they are extracted. They are mostly used for their aroma, either in the preparation of perfumes or to enhance the scent of the cosmetic product itself.

They have also been shown to have versatile antifungal, antimicrobial, anti-inflammatory and antioxidant properties, which is why they are often present in cosmetic formulations for skin and hair care.

In skin care products, essential oils are often found in mixtures with other active compounds. Since they are mostly composed of low molecular weight and lipophilic (oil-soluble) molecules, this allows them to penetrate the skin and are therefore used in combination with other substances that are not able to penetrate the skin on their own. They can provide the skin with nutrients and improve its appearance.

Essential oils instead of preservatives?

It is true that they have antifungal and antimicrobial properties, but if we wanted to ensure the stability of the cosmetic product, we would have to use larger amounts of essential oils than are permitted. Therefore, they are mostly used as auxiliary preservatives and can consequently reduce the concentration of other preservatives, but they are usually not used independently.

Are they safe?

Their safety in cosmetic products depends on many factors, including the quality of the raw materials and the extraction method used to obtain the essential oil. In addition, they must be stored in airtight containers and protected from light. This preserves their properties and prevents instability problems that could affect the formulation itself and its stability.

How are they obtained?

Essential oils are obtained by various extraction methods, and the choice of extraction method depends on the raw plant material. Extractions can be divided into two groups: conventional and innovative methods. Conventional methods include cold pressing, solvent extraction, distillation (steam and water), hydrodiffusion, and others.

Innovative techniques, however, avoid some of the drawbacks of conventional techniques. Newer techniques aim to shorten extraction times, reduce energy consumption, and reduce solvent use and carbon dioxide emissions. These include supercritical CO 2 extraction , ultrasonic extraction, solvent-free microwave extraction, and others.

Side effects

Essential oils can cause side effects, which are mostly mild, but in some cases severe reactions have still been observed. If used topically without dilution, they can cause irritation and/or erythema on the skin and mucous membranes, so it is recommended that they be used only in diluted forms.

Toxicity levels vary greatly among essential oils. Many are toxic even at very low concentrations due to the toxicity of their components. In other cases, many that are considered non-toxic can be toxic in people who have previously been sensitive to a particular essential oil.

A person's age can also contribute to the level of toxicity due to the effect it has on skin structure and metabolism, making the very young and the elderly more susceptible. The most common complications caused by essential oils in cosmetics are: contact dermatitis (contact and allergic) and photosensitivity.

The first table lists the most common allergens in essential oils, while the second table lists slightly less common ones.

 Phototoxicity

When we talk about phototoxicity, we are usually talking about extracts containing furocoumarins or furanocoumarins. The Scientific Committee on Consumer Protection (SCCS) has written an opinion on the aforementioned substances and concluded that they are safe up to 1 ppm (1mg/kg) in the final products. Examples of essential oils with furanocoumarins are: bergamot, grapefruit, lemon, lime, bitter orange essential oil and others.

Otherwise, essential oils are legally limited to concentrations that should not cause side effects unless we are allergic to a particular oil, and it is good to know which essential oils are sensitive to light and avoid using them if we go out in the sun.

Tisserand R, Young R. Essential oil composition. Essential Oil Safety. 2014;5–22

Abdul Aziz ZA, Ahmad A, Mohd Setapar SH, Karakucuk A, Azim MM, Lokhat D, Rafatullah M, Ganash M, Kamal MA, and Ashrad GM. Essential Oils: Extraction Techniques, Pharmaceutical and Therapeutic Potential – a review. Current Drug Metabolism. 2018;19(0) Schäfer UF, Schneele J, Schmitt S, Reichling J. Efficacy, absorption, and safety of essential oils. Dermatologic, Cosmeceutic, and Cosmetic Development: Therapeutic and Novel Approaches. 2007;401-418

https://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_102.pdf

https://ec.europa.eu/health/ph_risk/committees/04_sccp/docs/sccp_o_036.pdf