Understand your cosmetic products, for reasoned and reasonable use. To choose and use vegetable oils in your cosmetic routine, it is important to keep several concepts in mind. Because we always choose better when we know what criteria we rely on, Compagnie des Sens offers you a brief overview of the questions to ask yourself before choosing a vegetable oil in cosmetics!
The comedogenicity of vegetable oils
An oil is said comedogenic if it causes the formation of comedones. Comedones are all small imperfections that we can have on the skin such as pimples, microcysts or even blackheads. They appear when the skin produces excess sebum which ends up blocking pores. Combination to oily skin, and especially young skin, are generally the most prone to blackheads that we will find on the level of the sebaceous glands.
A comedogenic oil is therefore an oil which will promote the formation of these imperfections and consequently block pores long-term. However, these oils can very well be used from time to time and in particular on dry skins, to solve a specific problem such as wrinkles, stretch marks or simply to rehydrate the skin.
Each oil has a comedogenicity index which depends on 3 criteria: its freshness, its sensitivity to oxidation and its speed of penetration into the skin. The comedogenicity index of an oil varies from 0 to 5, index 0 being non-comedogenic and index 5 being very comedogenic. If these indices indicate the likelihood that an oil is comedogenic, it is also important to consider your skin type and therefore possible unexpected reactions. Oily to combination skin will therefore be advised to use oils with a low index between 0 and 2, while normal to dry skin can more easily use oils with indices between 0 and 5.
More details : choose your vegetable oil according to your skin type.
To choose your vegetable oils carefully, here is a small, non-exhaustive list of oils according to their comedogenicity index.
Oxidation of vegetable oils
Vegetable oils are often defined by their oxidative potential, this is a breakdown of fatty acids which make up the oil and which therefore go alter the quality of the oil. This oxidation can be caused by different factors such as oxygen in the air, light, interactions with the container or even heat. The oxidation of an oil can thus increase its comedogenicity index and train allergic reactions and the appearance ofimperfections in addition to a rancid smell when using.
More details on: oxidation of vegetable oils.
Dry or fatty vegetable oil?
When applying vegetable oil to the skin, it is possible to feel a greasy sensation, although the oil no longer penetrates the skin as well. This phenomenon is due to the fatty acid composition oil which brings it a more or less strong affinity with the skin. The stronger the oil's affinity with the skin, the faster it will penetrate and the less greasy you will feel to the touch. These are these penetrating vegetable oils which are called dry oils. Dry oils will mainly consist of omega 3 and omega 6 which penetrate the skin more easily, while fatty oils will be more made up of omega 9. The choice of vegetable oil will therefore depend on your needs, if you want to maintain matte skin, without feeling greasy, you need a dry oil. If the goal is rather to make your skin satiny, a fatty oil will be perfectly suitable.
Here are some examples of vegetable oils with a dry or oily feel:
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Dry oils: Grape seeds, Perilla, Evening primrose or Hemp.
Virgin or refined oil?
First cold pressed virgin oil refers to the method of obtaining the oil, which differs from that of refined oils.
A virgin oil is obtained by cold pressed, which is a simple, fast and ancestral extraction method. It is a mechanical extraction method, where oilseed fruits and seeds are pressed to directly extract the oil. This mechanism takes place at room temperature so as not to denature the fatty acids. A virgin oil from first cold pressing therefore corresponds to the first juice of the seed or fruit, without chemical treatment or refining. This is a gentle extraction method that preserves the oil in its entirety, for a product rich in vitamins, antioxidants and other unsaponifiables.
Unlike, a refined oil is obtained by a extraction method, using a solvent, often alcohol. Once this oil is obtained, it undergoes several treatments:
- Degumming which corresponds to the elimination of phospholipids in the oil, complexes grouping one or more fatty acids with other molecules;
- Neutralization, to make the oil lose its free acidity;
- Discoloration and deodorization.
All these steps often require the intervention of chemical molecules. This involves the destruction of certain essential fatty acids if the refining temperature is high, as well as the loss of the natural composition of the oil. Likewise, new components can be created, which are not necessarily beneficial for the skin or for the diet. Refined vegetable oils still have the advantage of being better preserved than virgin vegetable oil.
Be careful when you choose an oil, if the method of obtaining it is not specified, it is certainly refined!
The vegetable oils of Compagnie des Sens are virgin oils resulting from a first cold pressing of fruits, seeds, pips, for the vast majority.
What is the saponification index?
The saponification index (IS) is a value used during the saponification process of a fatty substance. There are two saponification indices, that for potash (KOH) and that for soda (NaOH). In chemistry, the saponification index corresponds to the mass of potash or soda in mg necessary to neutralize the free fatty acids and saponify the esterified fatty acids contained in 1g of fat.
In other words, the saponification index of an oil corresponds to the quantity in milligram potash or soda required to saponify 1 gram of this oil. Each vegetable oil has its own saponification index, in fact depending on the oil used the quantity of potash or soda will be different. This index thus makes it possible to characterize the oils.
Saponification is therefore a chemical reaction between a fatty substance (vegetable oil or butter) and a base such as potash (KOH) or soda (NaOH). There are two types of saponification, hot and cold saponification. Cold saponification is often preferred, since it allows all the benefits of the oils to be preserved and therefore produces a better quality soap.
This method is widely used in cosmetics and in particular for soap making. Indeed, the saponification index is important data for knowing the necessary quantity of strong base to add to saponify a vegetable oil or butter. Generally soaps made from soda will be hard, while those made with potash will be softer or even liquid.
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Bibliography
Work : de la Charie, T. (2019). Treat yourself with essential oils. Why and how does it work? Editions du Rocher.