Free radicals are constantly running around in our lotions, seeking out electrons to fill its valence shell. When we add an anti-oxidant, we provide that free radical with those electrons. The radical is content with its electron shell and bothers us no more! How awesome is that?
VITAMIN E is one of the main lipophilic anti-oxidants you'll find for bath and body products, and it's the most commonly used by homecrafters. It comes in four varieties of tocopherols and four varieties of tocotrienols. We will be focusing mainly on the alpha tocopherol, which is the one you're most likely to see in suppliers' shops.
Vitamin E is found in our stratum corneum and is secreted by our sebaceous glands to the surface of our skin. Studies have demonstrated - at least on lab rodents - that it sinks readily into our skin and can inhibit lipid peroxidation, which is like oxidiation of the oils on our skin! It has also been shown to reduce sunburn irritation in mice (which just shows you albino creatures and sunlight don't mix!).
The interesting thing about Vitamin E is it can lose its anti-oxidating power, so it's unable to contribute an electron to the free radical. But in an exciting redox process, it gets its electron back, so the cycle continues again. Ah, you have to love chemistry!
You can use it at rates as low as 0.01 to 0.05% in your creations or oils. I like to use it at 1% because it has such wonderful qualities for skin, but you can use lower amounts.
VITAMIN C, or ascorbic acid, is one of the most common hydrophilic anti-oxidants. It's present in high amounts in our skin, and it can chase away scurvy (arrr, be gone scurvy!). Unfortunately, it's not very stable and can be esterified with phosphates.
For our purposes, it works well with iron found in our water, specifically converting Fe(III) to Fe(II).
Honestly, although Vitamin C does have some nice properties for skin, given its instability, it's probably not the anti-oxidant to use most in a lotion. As well, it's hydrophilic, meaning it's going to hang out mostly in the water section of the lotion, and rancidity takes place in the oil part of our lotion.
Join me tomorrow for fun with the chelating agents - EDTA and citric acid!