Is a thicker product, like a body butter, more moisturizing?
What Are Lotions Anyways…?
Lotions and creams are emulsions, which means that they’re a mix of two or more things that do to not mix. Like water and oil.
Ingredients that dissolve in water, like ascorbic acid (vitamin C) are dissolved in to the water portion of the product and ingredients that dissolve in oil like ceramides are dissolved in to the oil portion. The two are then mixed together with the addition of an emulsifier. An emulsifier is a surfactant, it helps break down the globules of oil and water in to smaller “bubbles” and helps to keep them from seperating.
Early generation creams and lotions actually used traditional saponified oil soap and detergents like sodium lauryl sulfate to keep them emulsified. But this raised problems as detergents like sodium lauryl sulfate are irritants, and traditional saponified oil soap has a high pH.
Emulsifiers are needed in a lotion or cream, usually in small amounts…without them the product would separate!
Now these emulsions (the water and oil mixed with an emulsifier) aren’t very thick, an oil-in-water emulsion (where the oil is inside water bubbles) will have the thickness of milk. A water-in-oil emulsion, mayonaisse is an example, will be thicker, but feel greasy on the skin. Most commercial products these days are oil-in-water emulsions. You can usually tell when a product is a water-in-oil emulsion when the oil is listed higher up than water on the ingredient list. It also won’t “absorb” in to the skin as well as an oil-in-water emulsion.
So in order to make an oil-in-water emulsion product easier to apply, and to create a pleasing texture, thickeners are added . This not only has the benefit of making the product look more like what we’re used to, but it also helps keep the product stable. Emulsions won’t stay mixed forever, making the product thicker makes it harder for the oil and water to break apart.
These thickeners can range from basic things like corn starch to more elegant solutions like carbomer. Carbomer is a powder thickener that turns water in to a thick and clear gel, it was actually designed specifically for cosmetics!
Thickeners are generally used in low amounts, ranging between 0.01% to 1%.
Some thickeners can act as humectants and emollients, like stearic acid, but the majority of the moisturizing effect is going to come from the other ingredients in the product .
A Study Tells Us…
A study actually examined the moisturizing effects of 12 similar moisturizing creams, they were all made exactly the same way except the level of thickener. They wanted to study, empirically, whether or not a thicker cream meant it was more moisturizing.
What they found was that changing the amount of thickener had no effect on how quickly water evaporated from the skin. Interestingly, they also found that people applied a similar amount of product, regardless of how thick or thin it was.
What Does That Mean To Us?
What that means is that you can’t judge whether a product will be moisturizing just because it’s thicker. It’s possible to create a lotion that contains 1% oil that is thicker than a lotion that contains 30% oil.
If you want a more moisturizing product you have to look at the ingredients list on the back, the higher up an oil or other emollient (like dimethicone) or humectant (like glycerin) is on the list the more likely the product will be moisturizing.
Most formulators know that a consumer expects a more moisturizing product when it’s thicker, so they formulate accordingly. So when you buy something that’s thick and creamy, it’s likely that it’s high in moisturizers…but you have to understand that it’s not moisturizing just because it’s thick! Moisturizers generally don’t make a product thick, and thickeners generally don’t make a product moisturizing.
So again, don’t let the thickness fool you! If a runny lotion contains a high amount of oil, it will be more moisturizing than a thick body butter that contains barely any.