In this article we want to explain two very important characteristics of vegetable oils that will help us decide if choosing one or the other when we want to develop a cosmetic formulation.
These characteristics tell us about the different degree of oxidation of oils and their degree of comedogeny, which is very important to know when formulating cosmetics for oily skin.
OXIDATION OF OILS
A vegetable oil can lose its properties if the fatty acids it contains are broken down. Some fatty acids are more fragile than others. Under certain conditions they degrade and the vegetable oil loses its properties.
Among the main sources of degradation are: oxidation and heat. However, the oxidative potential of a vegetable oil or butter depends on the nature and concentration of fatty acids in it. In general, the more double bonds the fatty acid has, the faster its oxidation rate will be.
That is, saturated fatty acids: Stearic acid (cocoa butter), palmitic (palm fat), myristic, lauric (coconut butter) … have fewer of these bonds, mono-unsaturated fatty acids such as oleic acid (shea butter) are at greater risk, and polyunsaturated fatty acids, such as linoleic acid (safflower oil, evening primrose), are most likely to oxidize and degrade rapidly.
|OILS WITH HIGH CONCENTRATION OF LINOLEIC ACID||OILS WITH HIGH CONCENTRATION OF OLEIC ACID||OILS WITH A BALANCE IN OLEIC AND LINOLEIC ACIDS|
|Wheat germ||Shea butter||Jojoba|
Here you can see in more detail the concentration of fatty acids of some oils:
Safflower oil: 68-85% linoleic, 8-30% oleic, 4-10% palmitic
Evening primrose oil: 73% linoleic, 9% γ-linoleic, 8% oleic, 6% palmitic
Grape seed oil: 71% linoleic, 16% oleic, 7% palmitic
Wheat germ oil: 58% linoleic, 17% palmitic, 12% oleic
Hemp oil: 52% linoleic, 10% linolenic, 10% oleic, 6% palmitic
Rosehip oil: 44% linoleic, 34% linolenic, 14% oleic
Borage oil: 39% linoleic, 20% γ-linoleic, 18% oleic, 10% palmitic
Sunflower oil: 70-88% oleic, 3-20% linoleic, 3-6% palmitic
Camellia oil: 79% oleic, 7% linoleic
Hazelnut oil: 79% oleic, 12% linoleic
Shea butter: 73% oleic, 14% linoleic, 9% stearic
Apricot seed oil: 69% oleic, 22% linoleic
Sweet almond oil: 67% oleic, 25% linoleic, 6% palmitic
Avocado oil: 63% oleic, 16% palmitic, 10% linoleic
Carrot seed oil: 68% oleic, 11% linoleic
Olive oil: 55% oleic, 20% palmitic, 18% linoleic
Macadamia nut oil: 54% oleic, 21% palmitoleic, 8% palmitic
Sesame oil: 46% linoleic, 39% oleic, 9% palmitic
Argan oil: 42-48% oleic, 30-38% linoleic
Jojoba oil: 5-15% oleic, 5% linoleic
Coconut oil: 4-10% oleic, 0.95-12% linoleic
PROPERTIES OF THE DIFFERENT FATTY ACIDS THAT MAKE UP THE OILS
Oleic acid: It is very moisturizing, well absorbed, regenerative and anti-inflammatory.
Linoleic acid: Improves the skin’s barrier function, softens itchy skin and dry skin, retains moisture, and is anti-inflammatory.
Linolenic acid: Helps reduce acne, retains moisture, strengthens the skin’s barrier function, and is anti-inflammatory.
Gamma linolenic acid: Improves the skin’s barrier function, softens itchy skin and dry skin, retains moisture, helps acne-prone skin, absorbs quickly, improves skin flexibility and is anti-inflammatory.
Palmitic acid: Forms an occlusive barrier on the skin and protects it.
Palmitoleic acid: Prevents burns, heals the skin with wounds, scratches and is antimicrobial
Stearic acid: Improves moisture retention, increases flexibility and repairs skin damage.
SENSITIVITY TO OXIDATION OF DIFFERENT OILS OF VEGETABLE ORIGIN
In practice, this oxidation phenomenon is easily detected because it is responsible for changes in the appearance of vegetable oil (rancid odor, color change).
Certain factors accelerate this oxidation: oxygen, light (UV), contact with pro-oxidant metals and, above all, heat, which will act as a catalyst for these oxidative reactions.
Other factors will curb this phenomenon, in particular the contribution or natural wealth of the oil in vitamin E.
To stop the oxidation phenomenon as much as possible, it is essential to store vegetable oils in good condition. It is therefore recommended that “very sensitive” oils be kept in a cool place, preferably in the refrigerator, in a tightly closed bottle, protected from air and light or add vitamin E when receiving them.
When incorporating these oils into an emulsion, it is required to incorporate vitamin E or organic rosemary CO2 extract into the vegetable oil before heating them to prevent the resulting product from oxidizing quickly.
According to estimates, the following vegetable oils can be considered very sensitive to oxidation: Camelina, blackcurrant, knob, safflower, hemp, raspberry, evening primrose, rosehip, kukui.
We can consider as sensitive the oils of: Borage, cotton, nopal, gardenia of the Incas, wheat germ, Kalahari melon, nigella, grape seeds, passion fruit, sunflower, cucumber seed, rice …
And we can consider as insensient the oils of: Apricot, Abyssinia, almonds, argan, sea buckthorn, avocado, babassu, bayberries, baobab, burití, cocoa butter, calófilo, camellia, cupuaçú butter, jojoba, shea butter, coconut butter, mango butter, macadamia, neem, hazelnuts, Brazil nut, olive, castor, salt butter, or sesame oil …
OXIDATION SENSITIVITY OF DIFFERENT VEGETABLE OILS AND BUTTERS
|VERY SENSITIVE OILS||SENSITIVE OILS||INSENT OILS|
|Knob||Nopal or prickly pear fig||Almonds|
|Hemp||Wheat germ||Sea buckthorn|
|Rosehip||Grape seeds||Bay berries|
|Cucumber seed||Cocoa butter|
VEGETABLE OILS WITH SPECIAL TREATING PROPERTIES ACCORDING TO SKIN TYPE
Depending on the type of skin to which our cosmetic product is directed, we can select one or another type of oil. For example, oils with a high palmitic acid content can be interesting for the formulation of cosmetics for dry skin.
Oils with a high content of oleic acid, such as almond oil, may interest us to improve the penetration of other active ingredients of a cosmetic formulation.
The iodine index can also help us in this decision, since oils with a higher iodine index will have a higher risk of oxidation.
OILS AND OILS: THE DEGREE OF COMEDOGENY OF THE DIFFERENT OILS
As we announced at the beginning of our entry, another factor that can make us decide on one oil or another when preparing our formulations is the degree of comedogeny.
Logically, if we want to formulate a product to treat oily skin or skin affected by acne, we will try to avoid oils whose degree of comedogeny is high.
However, the term “oily” is not directly linked to comedogenesis per se. Not because something is oily means that we will have an oily face and excess in sebum, since there are non-greasy products that are comedogenic (especially those formulated with mineral oils derived from petroleum that cause occlusion of the pores of the skin), while there are numerous vegetable oils that do not cause these unwanted effects.
On the contrary, these vegetable oils are recommended for facial cleansing or to counteract acne problems. And although vegetable oils, in principle, are suitable for nourishing all skin types, we will avoid those more comedogenic (pore clogging) in oily and acne-prone skin. Among them, we will avoid: Coconut oil, avocado oil, sesame oil, evening primrose oil, cocoa butter and also wheat germ oil …
There is a scale that measures the degree of comedogenicity of the oils. It is known as the Comedogenic Scale. The comedogenic scale includes a gradation of zero to five in which oils with the lowest gradations (0 to 2) are considered non-comedogenic and oils with the highest gradations (3 to 5) are considered oils with the highest possibilities to clog pores and leave a greasy feeling on the skin, which, on the other hand, is highly recommended in the case of dry or dehydrated skin.
On the “cosmetics to test” page they offer a slightly different list:
Argan, safflower and hemp oils would be classified at level O for comedogeneity. This list also includes petroleum jelly and paraffin which, as you know, are mineral oils derived from petroleum and whose use we strongly discourage since they clog skin pores.
Classified at level 1 would be the oils of babassu, camellia, castor, grapeseed, abyssinian, rosehip, sea buckthorn, shea butter and mango butter, squalene (this popular oil composed of fatty acids derived from olive oil) , sunflower (be careful, not the kitchen one, but a cosmetic quality bio oil), and calendula oil, which is not an oil but a marigold macerate of calendula flowers in sunflower oil, normally.
Classified in level 2 would be the oils of almonds, apricot, evening primrose, borage, jojoba, olive, tamanu or calophyll, baobab and hazelnuts.
Classified at level 3 would be avocado, macadamia, cottonseed, corn and sesame oils.
Classified at level 4 would be coconut, palm, linseed, soybean and cocoa butter oils.
Classified at level 5 (very comedogenic) would be wheat germ oil.
In general, it is proposed to avoid the following oils classified as “very comedogenic” or grade 4 to 5 in cosmetic formulations intended to treat oily skin: Wheat germ oil, of course, but also coconut, palm, flaxseed, soybeans, avocado, sesame, corn, evening primrose and cocoa butter.
The following oils are also proposed as the most suitable for all types of face par excellence:
JOJOBA oil: Also called “liquid gold”. It is a type of liquid, non-greasy wax, which is identical to the sebum that we produce naturally, which makes it the ideal oil for all skin types.
ARGAN oil: This oil is ideal since its value on the comedogenic scale is 0. It repairs the skin, regulates sebum, prevents and improves acne and is excellent for scars.
Considering the different types of skins and their needs, the following types of oils are proposed:
Vegetable oils to care for sensitive skin: Sesame (soothing, nourishing, antioxidant), Shea (Nourishing, restorative, soothing), olive oil (soothing).
Vegetable oils to regulate mixed and oily skin: Jojoba (regulates sebum production and is antioxidant), hazelnut (Regulates sebum production and is firming), neem (is antibacterial, regulator and antiseptic) …
Vegetable oils to treat dry skin: Almonds, avocado (protective, restorative, moisturizing and antioxidant), wheat germ (restorative, revitalizing), shea butter (nourishing, protective), cocoa butter (nourishing, restorative, protective), mango butter (moisturizer, emollient, softener).
Vegetable oils for mature skin: Rosehip (regenerating, anti-wrinkle, anti-blemish, tonic and revitalizing), argan (antioxidant and anti-aging), shea butter (regenerating), evening primrose (activates circulation), avocado butter (antioxidant and anti-aging), olive oil and cocoa butter.
NON-COMEDOGENIC OILS SUITABLE IF YOUR SKIN IS ACNEIC
The oils that we classified as suitable are those of: Abyssinia, jojoba, grape seeds, hemp, rice bran, apricot, hazelnut and almonds.
As you can see in this list, we include almond oil and hazelnut oil, because, depending on the literature, they appear as suitable and with a level of comedogenicity of 2 that is always indicative because “each skin” is a different world and what works for one does not automatically mean that will do for another person.
In this way, and taking into account the factors detailed above, we can define some of the oils we use most commonly:
Almonds: Oil suitable for its composition in fatty acids (high oleic) to treat and hydrate dry skin, with a low sensitivity to oxidation and rancidity and with a low degree of comedogenicity that makes it a versatile oil suitable for almost everything type of preparations.
Argan: Oil suitable for treating mature, sensitive and oily skin due to its balanced composition of oleic and linoleic fatty acids and its low comedogenic degree. It is also not very sensitive to oxidation, which makes it a very useful multipurpose oil.
Hazelnuts: Oil with a high level of oleic acid that gives it great hydration capacity. Its low comedogenic level, however, makes it suitable for hydrating oily skin. On the other hand, it is an oil that is not very sensitive to oxidation, which gives it greater long-term stability.
And we would continue like this with the oils most frequently used in natural cosmetics such as: Avocado, borage, coconut, black cumin, camellia, sea buckthorn, raspberry seeds or wheat germ that we already know that, in principle, would only be suitable for treating mature and dry skin due to its high degree of comedogenicity.
However, the amount of vitamin E that this oil naturally contains makes it a widely used oil mixed with other vegetable oils in all kinds of formulations to which it provides vitamin E, avoiding rancidity and enriching cosmetic compositions.