Sunday, March 11, 2012
What have we learned so far about making products for our skin?
Our skin is made up of many layers, and the uppermost one is the stratum corneum. Moisturizing is all about preventing transepidermal water loss by trapping water against our skin through emollients. Hydrating is all about bringing water to our skin by attracting it through humectants. And occlusives make sure that these good things stay near our skin so we can be moisturized and hydrated. So when we create a moisturizing ingredient, we want something that will form an occlusive barrier between our skin and the world to keep the moisture in and the world and its nasty wind, cold, rain, snow, and sun out!
Humectants draw water from the atmosphere to our skin and help moisturize. When we attract water to our skin from the atmosphere or apply lotions containing water to our skin, the water dissolves the molecules found in the natural moisturizing factor or NMF, and they act as humectants in our skin drawing water from the atmosphere. (The major components of this NMF is sodium lactate, urea, and pyrrolidone carboxylic acid (or sodium PCA), all great humectants.) We've also learned that there is the potential for some humectants to draw water out of the skin if conditions get very dry. But we've also learned that using occlusive ingredients will prevent this potential from becoming a reality.
So we want to make our products with three main goals in mind...
1. Drawing water to our skin (humectants);
2. Creating a barrier so the water can't get out (occlusives); and
3. Using emollients to make our skin feel smooth and lovely (emollients).
I use these three concept in every lotion I make. I generally have a humectant in the water or cool down phase, and emollients and occlusives in the oil phase or cool down phase (in the case of silicones). If you take a look at anything other than the basic recipes, you'll see I always have humectants, occlusive, and emollients in my products.
An updated overview of our skin
What are penetration enhancers?
What's the difference between moisturizing and hydrating?
Does glycerin pull water out of our skin when the humidity is low?
Skin chemistry and types section of the blog