THE PENETRATING FACTS ABOUT SKIN
by: Daniel Thompson
Do cosmetics penetrate the skin?
The public deserves well formulated safe cosmetics when shopping.
The companies producing cosmetics work under incredibly strict guidelines that ensure consumer safety.
Does that mean no one will ever have an allergic reaction to a cosmetic product? Absolutely not. The variables which cause such reactions are far too numerous to deliver such a promise; however, cosmetics, for the vast majority of users, pose no real problems at all.
Taking all the hype surrounding so-called toxic ingredients out of the equation for a moment (because toxicity cannot be discussed without understanding dosage, exposure, and tolerance for various ingredients but this post is about how the skin operates, not about specific biology of individual people), it is important to understand how the skin absorbs topically applied solutions.
There are two words that are often used synonymously, which really ought not.
Penetration and Absorption.
These are not the same at all, even if we read headlines like:
"The skin absorbs x number of kilos of cosmetics each year."
"The skin absorbs a large percentage of cosmetics every day."
"The skin absorbs chemicals found in cosmetics."
To fully understand the difference between the two, and ultimately how that difference affects the safety of cosmetics, it is important to understand how the skin is comprised.
Skin is built in three layers: the epidermis, the dermis, and the hypodermis. These three layers are remarkable in what they can do—protect from elements, regulate temperature, contribute to nutrient uptake, prevent water evaporation from organs. The list is long and impressive.
The epidermis is actually comprised of many smaller layers—this is the part of the skin you can see. Its primary function is to prevent any penetration of foreign substances. The epidermis is actually the first line of defense in the entire immune system. The epidermis is very good at its job. If it wasn't, we would literally be affected by every fluid and substance with which we came into contact. What is important to note is that the epidermis is comprised of cells that are dead or very near the end of their life cycle. In fact, the very most outer layer of the epidermis is completely flattened, dead cells. Very little can penetrate this layer, let alone get into the deeper layers of the skin.
The dermis is living skin, and this is where proteins develop into tissue. This layer of the skin is where we produce natural UV protection, where blood cells pass nutrients through the skin, and, of course, where all the nerve endings are located.
The hypodermis is a fatty layer of skin that cushions the upper layers and helps regulate body temperature. This layer is where the skin attaches to the muscles.
Cosmetics, by definition of law, can only penetrate the epidermal layer. No over-the-counter cosmetic penetrates into the dermal or hypodermal tissue. This is important to note because this is where the distinction between penetration and absorption is made.
Penetration is defined as the relative representation of the amount of a topically applied solution as it exists between the top layer of the epidermis and bottom layer of the epidermis.
Absorption is defined as the percentage of said solution that breaks beyond the epidermal tissue and is able to reach the bloodstream in the dermal tissue.
Safety—as in the statistical likelihood of irritation, bio-accumulation, etc.—is determined based on the difference between these two factors.
In simple language, penetration of a cosmetic formula poses a low risk of hazard, but the more the skin absorbs a formula, this risk increases.
Topical cosmetics are designed to penetrate the skin, but not be absorbed by it. In fact, if topical cosmetics did indeed become absorbed, they would have little to no effect and would increase the risk of hazard. Think of it like this—antioxidants are only effective if they remain on the surface of the skin, as in not penetrate at all. If they were to become absorbed by the skin, they would offer no protection at all. With this said, there are other variables which affect penetration and absorption—molecule size, ability to dissolve, and carriers used in the formula. Cosmetics are formulated with molecule sizes were chosen to ensure the solution remains on the surface of the skin. Unless they are blended with specific carriers, to help slightly penetrate the epidermis (such as in the case with exfoliators), the vast majority of cosmetic formulas cannot penetrate beyond the top layer of the epidermis. Additionally, cosmetic formulas are designed to not dissolve in fat, which means they do not have the ability to break down into smaller molecules and penetrate beyond the epidermal tissue. Absorption is, therefore, arrested before it can begin, thus increasing the overall safety (or lack of risk) in using the product.
So, does this mean the body never absorbs cosmetic ingredients? Of course not. It can happen. The risk is then evaluated based on what happens after absorption occurs. This risk must take into account many new variables—how long the exposure persists, the composition of the formula, and, of course, the method of absorption.
The body can excrete foreign substances quite effectively, that is why, often, chemicals can be found in urine. This is proof that the body is actually eliminating any unwanted substances that may have been absorbed. What was the method of absorption? Cosmetics labels always have a statement on them saying, "For external use only." If the formula is ingested, the absorption and the associated risks of hazard are very different than if the product is used as directed.
Think of it like this—laundry bleach used as directed poses almost no risk of hazard; however, if you spill some on your skin it can penetrate and, if left unchecked, can be absorbed causing terrible adverse reactions. If rinsed immediately it is neutralized and poses almost zero risks of absorption and reaction. If that same amount of spilled bleach is ingested, the risk of hazard is seriously increased, because the method of absorption is more rapid and indeed dangerous.
Cosmetics work under these same principles. Used as directed they pose little to no risk from absorption. Used incorrectly, that risk is significantly increased.
It is far too easy to create news headlines touting the possible risks of cosmetics based on absorption than actually explain the difference between penetration and absorption. It is far easier to simplify a rather complex biological process to create scare tactic statistics rather than delve into the complexity of the research. It is far easier to malign cosmetics because they are seen as luxury goods than to actually show how companies work to ensure consumer safety.
The truth is, very little of anything applied to the surface of the skin can actually penetrate it and even less can be absorbed. Even when such absorption occurs, the body is incredibly efficient at protecting its homeostasis through elimination.
Cosmetics are safe when used as directed.