Oleic acid is not considered an essential fatty acid because our bodies produce it. Although oleic acid is actually found in our human sebum - you'll probably see jojoba and olive oil touted as being very close to sebum as a selling point - it can actually make the effects of the bacteria responsible for some types of acne (P. acnes) worse!
Oleic acid is also found in sea buckthorn (15 to 20%), grapeseed (15 to 20%), almond oil (61%), macadamia nut (56%), and camellia seed oil (77 to 83%). Avocado oil is very high in oleic acid (75 to 80%). It's found in decent quantities in rice bran oil (42%) and sesame oil (45%), so these are great choices if you want to have good levels of both linoleic and oleic acid.
It's also found in high quantities in mango butter (46%) and shea butter (40 to 55%, depending upon region), so these are good butters to add if you're trying to increase your oleic acid content.
So why do we care about oleic acid in our oils? Oils and butters containing oleic acid tend to be very moisturizing and regenerating to our skin. They often offer anti-inflammatory properties and some, like olive oil, mimic our natural sebum. They tend to be absorbed well by the skin, which offers softening and moisturizing effects.
Oils high in oleic acid will go rancid far less quickly than those high in linoleic or linolenic acids - notice the single double bond - so they might be better choices for creations you want to last a long time.
Join me for more about olive oil tomorrow!