same time, many conventional cosmetics claim they deliver collagen, vitamins, and minerals to feed
our skin. So do cosmetics really “get under our skin”?
In fact, beauty is skin deep. Human skin is a powerful absorption organ that seems to be constantly
hungry for anything that touches its surface. Just like a curious toddler, our skin grabs every available
molecule, every single drop of water, every lick of makeup, and every whiff of fragrance and takes it
to its cellular “mouth” to taste, chew on, and, most likely, ingest.
Oxygen, nitrogen, and carbon dioxide, as well as toxic pollutants, enter our skin via three doors:
sweat ducts, hair follicles and sebaceous glands, or directly across the stratum corneum. This ability
of skin to absorb chemical substances so they can be spread throughout the body is widely used in
medicine. Transdermal delivery drugs for motion sickness, cardiovascular disease, chronic pain,
smoking cessation, and birth control are already widely used.
According to new estimates, our skin can absorb up to 60 percent of substances applied to its
surface. Unfortunately, along with water, vitamins, minerals, and oxygen, skin soaks up potentially
carcinogenic ingredients that increase our risk of having cancer at some point in our lives—as if
breathing polluted air and eating chemicals was not enough!
To perform their magic, many cosmetic products need to push active ingredients deeper beyond the
stratum corneum, the uppermost layer of skin comprised of dead skin cells. Traditionally, it was
thought that hydrophilic (water bonding, or dissolvable in water rather than oil) chemicals do not
penetrate deep into skin, while lipophilic chemicals (oils or oil-in-water emulsions) diffuse deeper
inside the dermis.
Today, scientists know that the process is much more complicated. Various substances can
penetrate the skin using different vehicles, sometimes as simple as water. This is when penetration
enhancers, also called sorption promoters or accelerants, come into play. To deliver active
ingredients, they decrease the resistance of skin’s barrier. Some dissolve intercellular matrix, some
change the skin’s metabolism, and some damage or alter the physical and chemical nature of the top
skin layer.
Most common penetration enhancers include alcohols (ethanol), glycols (propylene glycol), and
surfactants. Liposomes, biomolecular spheres that encapsulate various chemicals from drugs to active
components of cosmetic products, also serve as penetration enhancers. The most common liposome is
phosphatidylcholine from soybean or egg yolk, sometimes with added cholesterol. Nanoparticles,
currently used to deliver sunscreens and vitamins A and E, can boost the skin’s permeability by up to
30 percent. Some penetration enhancers, such as transferomes, which are made of surfactants and
ethanol, are able to deliver up to 100 percent of the drug applied topically! The greater its alcohol
content, the deeper the solution is able to penetrate. Many essential oils have been reported to be
gentle yet effective penetration enhancers.
What happens when a potentially toxic substance passes the skin’s barriers? It ends up in blood
vessels and lymph ducts located in the epidermis and dermis layers. Skin cells get their nutrients and
excrete toxins thanks to an endless circulation of blood and lymph. Lymph, a colorless fluid made of
plasma, performs a vitally important drainage function since it provides white blood cells that
produce antibodies to fight infection.
As chemicals are absorbed, they enter the bloodstream and travel with lymph across the body, to
be eventually filtered out by the liver and flushed away by the kidneys. However, some substances
remain inside the body, adding to the systemic load that can accumulate for decades. Since the skin is
the largest organ in our body, it soaks up contaminants in much larger amounts than the intestines or