GLA can have anti-inflammatory effects on our body and skin. It helps with the conversion of linoleic acid into arachidonic acid (if you want to know more about this, check out the Wikipedia entry) and helps with the anti-inflammatory and immune systems in our bodies. In animal studies, GLA in the form of borage oil was effective in reversing epidermal hyperproliferation (skin cells proliferating too quickly) and increasing ceramide synthesis in guinea pigs (although they ate it, rather than slathering on a decadent lotion!) Evening primrose was not as effective. Ironically, in human studies, ingesting evening primrose oil shows good signs of treating eczema and skin irritation, although similar studies of borage with eczema didn't show the same results.
Applied to our skin, GLA can be a great anti-inflammatory, improving skin's protective qualities and helping repair the skin barrier faster than linoleic acid. Like the oils containing linoleic acid, GLA will help with itchy dry skin, act as a moisture retainer, and helps with acne prone skin. And GLA containing oils are absorbed quickly into the skin, increasing skin's flexibility and suppleness.
Evening primrose oil specifically has been found to reduce transepidermal water loss (TEWL) and increase stratum corneum hydration in normal skin, but it doesn't seem to help as much as borage oil with atopic dermatitis (chronic inflammation of the skin that causes an itchy, swollen, red rash).
GLA is found mostly in what I have called exotic oils - oils we don't tend to use in great quantities like we do the carrier oils mainly because they are freakin' expensive! Evening primrose, borage, rosehip, and blackcurrant oils are filled have good levels of GLA from 15 to 23%.
How much GLA should we use in our products? Unfortunately, this information is sketchy at best with no consensus. We have suggestions from manufacturers to use up to 10% evening primrose and 10% borage oil, but the studies just aren't there to suggest these amounts are correct.
Join me tomorrow for a few ideas on how to use GLA in your lotion recipes.