Essential Oils in Cosmetics

What Are Essential Oils?

Essential oils are the aromatic oils found in some plants that give them their distinctive scents. These oils are called “essential” because they capture the essence of the plant’s fragrance. They are volatile, meaning they can easily turn into vapour and be smelled. Essential oils are extracted from plants and used as ingredients in cosmetic products, and the oil is known as a ‘Complex Natural Substance’. Think of them as nature’s fragrant treasures. The way we extract these oils can affect what we get from them and their safety for use in cosmetics.

Types of Essential Oils

In the world of cosmetics, various ingredients are considered essential oils due to their role in adding fragrance to products. There are different types of ingredients which are all considered ‘essential oils’:

1. Essential oil: These oils are obtained by pressing or distilling plant parts, like lemon peel or lavender. Pressing is also called Expression. Steam distillation is generally used, but due to the high temperature of the steam isn’t always suitable.
2. Tincture: Fragrant materials are soaked in ethanol, like witch hazel.
3. Pomade: Fragrant components from delicate flowers that wouldn’t be able to withstand high temperature are absorbed into animal fats, though it’s not commonly used in modern cosmetics.
4. Concrete: Fragrant (waxy) materials are extracted using hydrocarbons or supercritical CO2. These are usually further processed to create absolutes.
5. Absolute: These are highly concentrated fragrant materials, often purified from pomades or concrete, like rose absolute.
6. Resin: Some, like myrrh, are directly obtained from the plant.

Different extraction methods can result in the same starting material having different names (and different components and scents). For example, orange blossoms can produce “orange blossom absolute” through solvent extraction or “neroli oil” through steam distillation; when rose is steam distilled it is called “rose essential oil”, but when produced using solvent extraction is it called “rose absolute”.

Essential Oil Safety

Using essential oils safely is crucial. Many essential oils have specific safety limits, and we also consider limits for certain components that may be present in them. Typically the safety of EOs and EO components is determined by RIFM (The Research Institute for Fragrance Materials). However, not all essential oils have been thoroughly assessed, so just because there isn’t a specified limit doesn’t automatically make it safe at any level.  The work done by RIFM informs the production of IFRA limits for the different categories of products that fragrance ingredients are used in.

Skin Sensitisation

One major concern with essential oils is that some of their components can sensitise the skin. Regulations may limit the use of oils. It is important for the safety assessor to be aware of the components in an essential oil, because sometimes the components have a specified limit, which would then limit the use of the essential oil to ensure safety, even though the essential oil doesn’t actually have a specified limit.

Phototoxicity

Certain essential oils or their components are known to cause skin sensitivity when exposed to UV light. This is why there are specific limits for products that might be exposed to sunlight, especially sun protection products.

Systemic Toxicity

Possible toxicity to the body cannot be ruled out and also needs to be taken into account.  A common component of a number of EOs is called methyl eugenol (ME). This does not cause skin sensitisation but it is a suspected carcinogen. It is therefore tightly limited in cosmetic products. The EU/UK Authorities have limits of ME in the finished product: 0.0002% in leave on products. 0.001% in rinse-off products, with higher amounts permitted in Eau de Toilette and Eau de Parfum (0.004%, 0.01% respectively).  IFRA has issued different limit for the various product categories, but all are less restrictive than the EU limits, except for baby skin products – category 5D (0.000069%) and ano-genital products – category 8 (0.000069%).

There are other essential oils that may also be limited in the safety assessment due to a low margin of safety for systemic toxicity, due to components in the oil.  This type of toxicity is taken into account when doing the safety assessment, and since 2020 IFRA also includes systemic toxicity in their calculations as well as the more common issue of skin sensitisation.

General Guidelines for Safe Use

To ensure the safe use of essential oils in cosmetics, here are some general rules:

• Use a maximum of 1% total essential oils in face products.
• For body products, the limit is 2% total essential oils.
• Bath or rinse-off products can contain up to 5% essential oils.
• Baby products should have a maximum of 0.25% essential oils, preferably less volatile base-type oils.
• Consider adding antioxidants like tocopherol, rosemary leaf extract, or BHT to products with essential oils that contain limonene, linalool, pinenes, terpenes, as they can potentially oxidize and cause skin sensitivity (these are pines oils or citrus oils typically).

Most essential oils are OK for any product at 1%. The following table lists some common ones that have restrictions either directly defined by IFRA or due to certain components found in the oil. The actual limit will depend on what type of product it is, but the limit for a leave-on body product and a rinse-off product are given as examples.