Fatty acids are absolutely necessary for healthy skin (and healthy everything else, technically). Some people, especially ones raised in a Western beauty ethos, tend to equate “oil” with “clogged pores” and are drawn toward products that boast “oil-free”. That's a mistake. Your skin requires oil of many different kinds, especially those of us with dry skin.

Fatty acids are lipid molecules with long, skinny carbon chains. They play a lot of roles in skin function; one of the most important is in the stratum corneum, which is the outermost layer of your skin. The stratum corneum is set up like a brick wall, with bricks made of corneocytes and mortar made of a lipid (fat) matrix, filling in the gaps and holding everything together.

That lipid matrix is composed of about 50% ceramides, 25% cholesterol, and 15% free fatty acids. PLUS, ceramides themselves are made of fatty acids tethered to a sphingosine base. Fatty acids are absolutely crucial to the proper function of your stratum corneum, keeping the outside on the outside and your insides on the inside.

There are two types of fatty acids: essential fatty acids, which means your body needs them but can’t produce them itself, and non-essential fatty acids, which your body can produce just fine on its own. There are only two essential fatty acids: linoleic acid and alpha-linolenic acid. I’ll only address linoleic in this blog post, because alpha-linolenic is more something you get from your diet.

There are five major types of fatty acids you’ll get from skincare products. Most plant oils contain most of these fatty acids, just in different proportions. I’ve listed them in my own unofficial and at best semi-scientific order from “sure, I’ll put that on my skin” to “the light, the truth, the way”.

PALMITIC ACID

Along with stearic acid, palmitic acid is one of the two saturated fatty acids. Remember how fatty acids are long, thin molecules? Saturated fatty acids are completely straight, like a toothpick. That means they can get closer together than the kinked and bent unsaturated fats, increasing their overall density. That’s why saturated fats tend to be solid at room temperature (like shea butter), while unsaturated fats are liquid (like olive oil).

Palmitic acid is a rich emollient as well as an occlusive agent, meaning it locks moisture into your skin rather than letting it evaporate. It’s a perfectly good ingredient, although it isn’t found in high levels in many oils you’d use on your skin.

Found in high levels in: palm oil (thus its name), sea buckthorn berry oil, neem oil

STEARIC ACID

Stearic acid is the other saturated fatty acid. Like palmitic acid, it’s very rich and forms an occlusive layer over the skin. An interesting note: stearic and palmitic acid levels are up to 31% lower in aged skin compared to young skin, so there may be an anti-aging element to these two ingredients.

Found in high levels in: butters like cocoa, mango, and shea

OLEIC ACID

Derived from the word “olive” because it’s found in such high quantities in olive oil, oleic acid is a very rich moisturizer. To some, it’s a powerful and luxurious way to pack in the hydration; for others, especially those with acne or easily-aggravated skin, it can be a comedogenic nightmare. As always, your mileage may vary, so patch test some products or straight oils high in oleic acid and see how your skin does.

Found in high levels in: avocado oil, olive oil, sweet almond oil

LINOLEIC ACID

Now we get into the really good stuff. Linoleic acid is an essential fatty acid – your body can’t produce it by itself – so you need to get it either from things you eat or things you put on your face.

There’s a long, long list of the great things linoleic acid can do. Here are some of them:

• Walk back damage from UV radiation
• Increase barrier function
• Reduce hyperpigmentation
• Increase circulation
• Fight acne
• Even skin texture and reduce scaliness

So why isn’t linoleic acid in every single thing we put on our face? Two reasons: oils high in linoleic acid are generally pretty expensive, and they have a very short shelf life – often less than 6 months before they oxidize and go bad.

Found in high levels in: sunflower oil, safflower oil, soybean oil, hemp seed oil, wheat germ oil

GAMMA-LINOLENIC ACID

GLA has a lot of the same great effects as linoleic acid, plus it can reduce inflammation and increase ceramide synthesis (which, as mentioned above, form 50% of the lipid matrix in the stratum corneum). It’s a relative of linoleic acid and another essential fatty acid that you need to get from your diet/skincare regimen.

Found in high levels in: rosehip oil, evening primrose oil, borage oil