Plant oils and sensitive skin

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?

First - backtrack to 2016 when I starting working with Cosmetic Chemist Amanda Foxon-Hill of Realize beauty, with the brief of creating the most gentle cleanser possible. I came to her with ideas about what ingredients we might want to use. Some of those ideas held up to scrutiny, while others didn't. I realised then how much complexity and nuance is lost on the internet - nothing beats speaking to an expert.

One of the things I ended up doing u-turn on was the list of oils I'd wanted to include. I had thought that oils high in Oleic acid were the 'bad guys', as oleic acid is a well-known penetration enhancer, while linoleic-rich oils like hemp and grape seed oil were the skin barrier friendly heroes. Amanda, however, advised otherwise.

 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. 

If free oleic acid is 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 oxidize they change chemically, creating by-products which could then add to the irritation potential. 

That's not to say that these oils should be avoided. If you've ever experienced irritation from plant oils though, it might be something to consider.

Stability heroes

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 more delicate oils in there too. 

Do you have a favourite oil for sensitive skin?

If you'd like more information, Amanda Foxon-Hill writes about the oleic acid/ triglyceride topic here. There's a handy chart here courtesy of New Directions in Australia with more info on free oleic acid levels in plant oils. Labmuffin also talks here about fatty acids in oils.

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