The use of oils for cosmetic purposes is not recent. Some documents show that Egyptians and Romans used natural oils for cosmetics, like making perfumes, protecting the skin or mixing them with mineral powder to produce makeup.
We are now tending to go back to natural cosmetics, and nowadays, it is easy to find products containing natural oils. In this post, we will see why natural oils are essential in skincare, the main oils and butter used to prepare formulation and their benefits to the skin.
Why are natural oils beneficial for the skin?
Our skin is covered by a layer which protects it against external aggressions, weather conditions, microorganisms, etc. This layer is called the Hydro Lipid Film, mainly made of water, sebum, other lipids and sweat.
The natural oils have a lipid composition similar to the hydrolipid film. Due to this similarity, natural oils can easily penetrate the skin barrier and reach different skin layers. They also help to strengthen the skin barrier and, therefore, improve skin health.
Differences between oil, fat, butter and wax
When talking about natural oils, people need clarification with the terms oil, fat, butter and wax. They are all part of the same group of Lipids that contain different properties which benefit the skin.
Among the four categories, wax is the central concept. Chemically, wax is an ester of fatty acid and a long-chain alcohol. It is important to note that wax contains only ONE fatty acid per molecule; therefore, wax is a mono-glyceride compound.
Waxes can create a protective layer on the skin and are humectant, and these two combined properties allow the wax to lock moisture in the skin and keep it moisturised.
On the other hand, oils, fats and butter are triglycerides, which means that they combine a glycerol molecule with three fatty acid chains. The differences between them come from the melting point (to be more precise, from the titer point, but we will simplify to the melting point as they are similar and melting point is easier to understand).
Based on the melting point, we can define fats, oils and butter as follows:
Fats are triglycerides with a melting point over 40.5 degrees Centigrade and, therefore, are solid at ambient temperature. One example of fat is lard.
Oils are triglycerides with a melting point below 20 degrees Centigrade and are liquid at ambient temperature. Examples of oils are olive, sunflower or rapeseed (vegetable oils).
Butter is a triglyceride with a melting point between oils and fats, 20 and 40.5 degrees Centigrade. A typical example of butter is cocoa butter.
I am not going deeper to explain that, as this topic deserves a complete chemistry lecture. Still, the difference in the melting point is a consequence of the fatty acids in the triglyceride. Two aspects of the fatty acids influence the lipid melting point: the number of carbon atoms and double bonds in the fatty acid chain.
Natural Oils vs Essential Oils
Another confusing point for some people is the difference between natural and Essential Oil. Of course, both have a natural source, and both are lipids, but here are their unique common points.
The main difference between them comes from the chemical composition. As I previously mentioned, natural oils are triglycerides, one type of lipid. Essential oils also contain lipids, but they are very different. Essential oils contain volatile lipids, mainly terpenoids, but don't contain triglycerides.
Another difference between natural and Essential Oil is the extraction process used to obtain them. As we will see later, natural oils are usually obtained by the mechanical press of some seeds or fruits. In contrast, essential oils are extracted by distillation of the right part of a plant (from leaves, flowers, roots etc.).
The main difference is that natural oils can be directly applied to the skin. However, you cannot do that with most essential oils; they must be diluted with a carrier oil (usually a natural oil) before applying them to the skin.
Which are the most frequently used natural oils in cosmetic products?
The list of natural oils used in cosmetic product formulation is enormous. Some are well-known, such as Olive Oil, Sweet Almond oil or Shea butter, while others are a bit more strange (see Andiroba oil, for example). I cannot talk about each natural oil, so I will focus on the most commonly used in cosmetics.
Coconut Oil
Coconut oil (INCI Cocos Nucifera Oil) is obtained from the fruit of a palm tree originally from the South of Asia. Coconut oil is a colourless oil in the liquid phase (above 30 Degrees Centigrade) and white in the solid phase below 30 Degrees Centigrade, and it has a soft coconut smell. Coconut oil has different uses, from cooking to cosmetics.
Coconut oil can be obtained by two processes, producing virgin coconut oil with the same properties. These two methods are the hot and cold press of the coconut, and the cold press method allows the extraction of coconut oil with more nutrients and, therefore, higher quality.
Composition
Coconut oil contains mainly saturated fatty acids (exactly lauric and myristic acids). The fatty acids are not the unique ingredients in the coconut oil composition; they also have other components like minerals, proteins, sterols and vitamins, mainly vitamin E.
Benefits
The main benefits of coconut oil for the skin are:
It is occlusive. Coconut oil is a high-density oil that allows it to create a lipidic layer over the skin, and this layer prevents water loss and, therefore, keeps the skin moisturised.
Coconut oil has anti-bacterial and anti-fungal properties due to the presence of laurin and capric acids. The application of coconut oil prevents skin infections.
Anti-wrinkle properties. Coconut oil is rich in antioxidants like vitamins E and K and minerals such as calcium, iron and manganese, which help with skin regeneration.
It is protective. Coconut oil is a fantastic ingredient to fight free radicals and prevents oxidative damage due to the high amount of antioxidants it contains.
These are the main properties of Coconut oil, but they are not unique. Coconut oil helps to balance the skin pH after cleansing, soothes sensitive skin, helps to treat psoriasis, and accelerates the tanning process.
Sweet Almond Oil
Sweet almond Oil (INCI Prunus Amygdalus Dulcis Oil) comes from almond tree seeds, and this tree is typical of the Mediterranean areas. Almond Oil is a deep yellow, odourless Oil, liquid at ambient temperatures and solid below -18oC.
After harvesting the Almond, the inner seed is separated from the nutshell and dried. Almond Oil is obtained from dry almonds through three different processes:
• organic solvent extraction
• supercritical fluids extraction
• cold press
The almond Oil obtained through the cold press process is high quality and contains numerous nutrients.
Composition
Despite the name, Sweet Almond Oil has a low sugar content. The main compounds in this Oil are water, lipids, proteins, and minerals, among others.
90% of the lipids contained in sweet almond Oil are monounsaturated fatty acids (oleic and linoleic acids). Sweet almond Oil contains other essential nutrients, like tocopherol (vitamin E) and phytosterols (b-sitosterol). It includes proteins like amandine and carbohydrates such as cellulose, hemicellulose and starch. It contains vitamins from group B (B1, B2, B3 and B6) and minerals (potassium, phosphor, magnesium, and calcium).
I want to highlight the presence of some essential antioxidants for skincare in Sweet Almond Oil: ferulic acid and resveratrol.
What are the cosmetics that contain Sweet Almond Oil?
You will find Almond oil in moisturisers and emollient creams, as well as in hair products and makeup removers. Sweet Almond Oil is present in cosmetics in two ways: as part of an emulsion (concentration 1-5%) or as a vehicle (up to 80-90% concentration).
Any product containing Sweet Almond Oil must include preservatives. Sweet Almond Oil decomposes quickly through the rancidification process, producing a terrible smell, and the effect can harm the skin.
There are other parts of the Almond used in cosmetics. The ground almond (INCI Prunus Amygdalus Dulcis Seed Meal) and ground almond shells (INCI Prunus Amygdalus Dulcis Seedcoat Powder) are added to some cosmetics to produce scrubs. The most commonly used is nutshell powder, as ground Almond allows for gentle and soft skin exfoliation, which is vital for people with sensitive skin.
Benefits
The main benefit of Almond Oil is its highly emollient property. It has a high oleic acid content which locks moisture in the skin and helps to strengthen the natural skin barrier.
A significant property of Sweet Almond Oil is that it helps other ingredients to penetrate the skin. The oleic acid in the Almond Oil interacts with the lipids in the Stratum Corneum, making this layer more fluid; other elements can penetrate it easily. That is why Almond Oil is used as a vehicle for other active ingredients.
But these are not the unique benefits of Almond Oil. Here are a few more:
• Prevents the skin from ageing
• Protects the skin against free radicals
• Induces collagen and elastin production
• Soothes skin irritation
• Avoids dandruff formation
• Hydrates the hair.
Olive Oil
Olive Oil (INCI Olea Europaea Fruit Oil) is one of the oils used for the longest time and before Christ's era for food, fuel, and religious and cosmetic purposes. In the 7th century BC, Homer referred to Olive Oil as "liquid gold".
Egyptians also used olive oil as part of their rituals. Scholars have found pots containing olive Oil in Ramses II's tomb.
Olive Oil comes from the cold press of the olive, a fruit produced by the olive tree, typical from the Mediterranean area (Spain, Italy and Greece mainly). Different factors influence the quality of olive Oil, like the variety of olive, type of extraction, way of harvesting, transport conditions, etc.
Composition
Olive Oil Oil is rich in fatty acids, mainly oleic, palmitic, and linoleic. It also contains vitamin E, phytosterols, carotenes and chlorophyll. The high content in squalene, up to 77% of the non-saponifiable fraction, is worth noting, which has fantastic properties for the skin.
Uses of Olive Oil
Olive Oil has different uses in cosmetics and can be used as an active ingredient and as a vehicle.
Olive Oil as a vehicle
Olive Oil is the most frequently used oil in the preparation of oleates, and it is also frequently used as a vehicle in different massage and therapeutic oils.
Olive Oil feels greasy when you touch it, making application easy. It is not very sensitive to oxidation due to the high amount of vitamin E. Its high oleic acid content favours the penetration of other ingredients. Olive Oil is what we call a penetration enhancer.
Olive Oil as an Active
The main functions of Olive Oil as an active ingredient are emollient and moisturiser. Olive Oil reduces transepidermal water loss creating a protective layer over the skin, and the squalene contained in Olive Oil increases the strength of this protective layer. After applying Olive Oil, the skin feels soft and luminous.
Other benefits of Olive Oil for the skin are:
• Cleanses and nourishes the skin and is present in cleansing balms and oils.
• Due to the high concentration of vitamin E, it is a good antioxidant.
• Hydrates as it contains tocopherol, monounsaturated fatty acids, and minerals.
• Helps to strengthen the nails.
• Reduces dark circles and fine lines in the eye area.
In this post, we've talked about some of the most common oils used in natural skin care products, but there are many other oils. We will be posting shortly about the rest of the most frequently used oils and plant & seed butter in natural cosmetics. However, if you'd like information on the benefits of any other oil, butter or ingredient in general, please let us know in the comments section below or email us. We will include it in our next post.
Dr Irene Resa
Bioanalytical Chemist