May 9, 2017
The Baobab is known as the ‘Tree of Life’ - it can live for thousands of years, with oil extracted from the fruit rich in vitamins and the amino acid lysine.
It may, however, be less suitable for very sensitive skin. Why is this?
Fatty acids in plant oils most typically start off in life as part of a triglyceride, with three fatty acids attached to every glycerol, as in the drawing above.
However if that structure breaks down, the fatty acids become free - the bottom diagram. Free fatty acids can also be present just because they didn't form part of a triglyceride in the first place. Either way, free fatty acids can be an issue if you have very sensitive skin.
Free oleic acid
When oleic acid is free, it's able to penetrate deeper into the skin, disrupting the protective barrier in a way that isn't possible when it's part of the larger triglyceride. This is isn't necessarily a bad thing for everyone - it can help to deliver actives deeper into the skin, and is used in pharmaceuticals to do exactly this. However, skin barrier disruption is something to be avoided if your skin is easily irritated or you're prone to eczema.
Knowing that free oleic acid can be a problem, it might seem logical to avoid oils high in oleic acid. However, a high oleic acid content doesn't mean that it's high in free oleic acid, and vice versa. At 40%, the Baobab oil above isn't one of the oils with the highest oleic acid content, yet it's free oleic acid value can be up to 20% of the total.
Meanwhile Apricot kernel and Camellia oils have a higher oleic acid content - closer to 60%. Yet their free oleic acid values are typically a tiny 1% or under. Their relative stability means that free fatty acid content isn't likely to increase dramatically over their shelf life either. All of this means they're likely to stay in their triglyceride form, and so less likely to cause skin barrier disruption, making them an excellent choice for sensitive skin.
High linoleic oils
While studies suggest linoleic acid is ideal for sensitive and atopic skin, these oils tend to be more delicate and prone to oxidisation. When ingredients oxidise, they change chemically, creating by-products - some of which can create irritatation. That's not to say that these oils should be avoided, but if you've ever experienced irritation from plant oils, it's something to consider.
On the other side of the spectrum are Meadowfoam seed and Jojoba oils - superstars of resilience. Alongside their multiple benefits, their unusual structure of long-chain fatty acids means they're amongst the most stable plant oils available. The good news is they'll up the stability of the oils around them, so you can use small amounts of more delicate oils in there too.
Do you have a favourite oil for sensitive skin?
Update: If you'd like more information on which oils are low in free oleic acid, there's a handy chart here courtesy of New Directions in Australia. There's also a video by Labmuffin here which gives a more in-depth look at fatty acids in oils.