Saturday, July 31, 2010
The chemistry of our nails: Lecithin
The soy and the egg lecithin do differ a little. The soy has a fatty acid profile of 20% palmitic acid (C16), 4.3% stearic acid (C18), 11.4% linoleic acid (C18:1), 56.6% linolenic acid (C18:2), and about 7% linolenic acid (C18:3). The egg lecithin contains 30% palmitic acid (C16), 15.9% stearic acid (C18), 26.4% oleic acid (C18:1), 16.2% linoleic acid (C18:2), and no linolenic acid. It does, however, contain arachadonic acid at about 6%. Both of these contain little to no Vitamin E, but they contain B vitamins (choline, Vitamin B8), and they contain 60% to 70% phospholipids (made up of the fatty acids listed above). Most of what we find on our suppliers' shelves is the soy version of lecithin, but if you're vegan or have any restrictions on your diet, ask before buying.
Choline has been shown to increase skin hydration, so it can act as a humectant to bring water our skin. In one study, the application of lecithin to skin increased water retention by 40% and it lasted about 2.5 hours! Another ingredient in lecithin - inositol - has been shown to decrease trans-epidermal water loss in animal studies. It's also been shown to increase moisture retention in our hair. And it's an anti-oxidant - it's three great things in one!
Lecithin is considered a great moisturizer with those high levels of oleic and linoleic acids, which will moisturize and help restore a damaged skin barrier. The stearic acid is also very moisturizing!
rancidity at 0.01% to 0.25%. It can help boost the efficacy of Vitamin E and Vitamin C as anti-oxidants (science isn't really sure why this is...)
Lecithin can be used in myriad ways in our formulating. It can be used in balms to act as a moisturizer, emollient, and protector. It can be used as a co-emulsifier in the HLB system (check with your supplier as it could have an HLB of 4 or 7, depending on how it is processed). It can be used wet oxides for mineral make-up if you want to press your eye shadows!
When it comes to nail care, lecithin is a Viking! It works well at low levels to moisturize our nails and help return some of those phosopholipids to dry and brittle nails!
One of the down sides of lecithin can be the smell. It can get a fishy odour at around 49˚C and will smoke at 70˚C, so you want to melt this stuff in a double boiler, not the microwave where you can't judge the temperature. You only want to heat lecithin slightly - never ever take it to the heat and hold stage or you'll get a horrible stench, so add it as you're about to take your oil phase out of the double boiler and mix it well.
The lecithin I purchased from Aquarius is a sticky brown liquid that I can add at room temperature to various anhydrous products. (It's really inexpensive - $4.00 for 250 ml or 8 ounces). And you can include it in any of your products as up to 10% as an oil. (You can use more, but it does have kind of earthy scent that might annoy some people). It is oil soluble, so you won't be putting this into any of your toners or skin refreshers!
Join me tomorrow for fun with lanolin!