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.
This all sounds like it should be good for us, so what is it which makes this oil less suitable for very sensitive skin?
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, 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.
So should the sensitive skinned just avoid oils high in oleic acid?
It's actually slightly more complicated than that.
A high oleic acid content doesn't necessarily = more free oleic acid, and vice versa. The Baobab oil above isn't one of the oils with the highest oleic acid content at 40%, yet it's free oleic acid value can be up to 20%.
Meanwhile Apricot kernel and Camellia oils have an oleic acid content closer to 60%. Yet their free oleic acid values are typically less than 1/20 of the amount found in the Baobab, at 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 unlikely 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, the sticking point here is that these oils tend to be more delicate and prone to oxidisation. Stability is a key requirement when it when making any products but even more so when it comes to making ultra-gentle skincare. Choosing less resilient ingredients risks reducing that stability. 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 makes them 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.
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.
Do you have a favourite oil for sensitive skin?