Does Skin Absorption Matter?

Slather on that sunscreen, relax in a long hot bath, or douse yourself in body spray. There are many products we use every day, ingredients of which end up in our bodies. But skin absorption rates are still largely unknown and varied. And the real surprise is that skin absorption may not be as important as we think--reactions that occur invisibly in the skin can affect the entire body.

You'll see claims on different websites like this:

"Up to 70% of what we put on our body is absorbed in to our bloodstream."
"Upwards of 100% of what we put on our skin ends up in the body."

While we, of course, know that chemicals applied to the skin are absorbed in to the bloodstream, these claims of certain percentages are actually largely un-substantiated. Surprisingly, there has been no study that inclusively details the average amount of a typical cosmetic formulation that ends up in the bloodstream. (And know that when I say "cosmetic" I don't just mean makeup. I mean lotions, shampoos, deodorants--everything you put on your skin.) Numerous studies have found traces of many cosmetic chemicals in breastmilk, urine and blood, indicating that cosmetic chemicals do end up in the body. But as for one definitive study or collection of studies that would enable a claim of "x% is absorbed," there is none.

Let's also take a look at the meaning of a statement like this. When you say 70%, does that mean if you apply 1 ounce of a lotion to your body, 70% of that 1 ounce would be absorbed, or does that mean, of the ingredients list, 70% of the listed ingredients would be absorbed in some amount? Where this claim came from is unknown, but it started online and has become a cornerstone marketing point for "green" companies everywhere.

Dependent Upon Blend of Ingredients
No cosmetic formula is created exactly the same. Even products with similar ingredients are absorbed in to the body differently. The amount of water in the formula, the viscosity, presence of penetration enhancers like glycols, the presence of nanoparticles, pH, the particular chemical makeup--all of these factors will affect how a product is absorbed.

Dependent Upon Usage
Typically, leave-on products like lotions will usually have higher absorption rate than a wash-off product like a shampoo, just for the sheer amount of time and surface area that you're exposed to.

Dependent Upon Age
As we age, our skin becomes thinner and it is theorized that absorption can increase. Also infant skin is thought to be thinner and/or more absorbent as well. (This study found that infants absorbed more phthalates than adults.)

Dependent Upon the Area of the Body
Obviously, the skin on the soles of our feet is much thicker than the skin on our faces, so where the product is applied has a big effect on absorption. Additionally, an area of skin that is not touched much by clothing has the potential to absorb more than an area where clothing would rub a product off the skin.

Absorption Not As Important as We Thought
While the actual absorption of cosmetics is not known, and varies wildly from person-to-person and from formula-to-formula, this does not support the argument that synthetic chemical formulas are safe. Proponents of these synthetics will say that the percentage of ingredients absorbed in to the body are so small that they don't have an effect on our health. But they're completely missing the point...

The skin IS the body. It's not a disconnected external shell. It's an organ that interacts with the rest of the body.

Several studies have found that when certain chemicals are applied to the skin (parabens, triclosan, phthalates) they interact with an enzyme called SULT1E1. This enzyme is what's responsible for flushing estrogen out of the body. These chemicals have been found to inhibit the activity of this enzyme, thus possibly increasing estrogen levels in the body. (For more details on this, check out my article here.) It's kind of like clogging the drain that allows the estrogen out. If the bathtub keeps running, and the drain continues to clog, at some point it's going to overflow. With an increasing problem of women and men having problems with estrogen dominance syndrome, many natural healthcare professionals and scientists alike agree that estrogenic chemicals applied to the skin can partially be to blame.

So, while absorption rates are still largely unknown and varied, absorption is almost secondary to reactions that actually occur in the skin and that can affect the function of the rest of your body.