How toxins get into our bloodstream
The skin is our largest and one of our most important organs. It does the indispensable job of keeping us cool and protecting us against the elements. The only downside to having it is that we have to endure a phase during puberty in which it becomes a pimply repellent against the opposite sex.
But what happens when the skin is not able to carry out one of its key functions? What happens when chemicals manage to break our skin’s defences? Is it possible, for example, for the cosmetics we put on our skin to make it into our bloodstream and cause damage from there?
There are three layers to our skin:
- a top layer (epidermis),
- a middle one (dermis)
- and an inner one (hypodermis).
As you might expect, the top layer is our first line of defence, it has a fat buffer and many blood vessels inside it. This layer is lipophilic (oil-loving) and hydrophobic (resistant to water), a feature which accounts for the fact that we do not fill up with water every time we step into the shower or swim in the ocean. Oils typically make it into the upper layer (penetration) but this is most often as far as they go. The other layers further below have a different chemical composition, making it more difficult for oil to go any deeper.
This means that most oils won’t make it into your bloodstream. There’s too much water in our bodies and too many layers of cells to prevent this. But does this mean that we don’t have to worry about chemicals in our cosmetics? Not quite.
The cosmetics industry has found clever ways of getting past these epidermal security guards: Through a process called emulsification, oil and water are mixed. It’s a bit like how mayonnaise is made — the blending of a water-based ingredient (mustard and lemon juice) with an oil is achieved using an egg yolk, which binds them. Modern cosmetics function similarly. They use emulsifiers to blend oil and water, making it easier to penetrate your skin.
What about the skin’s defences?
The good news is that the skin is savvy enough to deal with even the intruders that come through with emulsifiers. Also, many molecules are simply too big to get through. Others remain on the skin’s surface and still others bind with the skin itself. Those that do seep through will encounter enzymes that break down or inactivate toxic chemicals. There are however some that may do the opposite, i.e. they activate chemicals, making them more toxic. For example, in 1775 Percivall Pott, a British doctor, found that contact with polycyclic aromatic hydrocarbons in soot was causing chimney sweeps to get cancer.
Absorption and penetration
When it comes to chemicals in cosmetics, it is important to distinguish between penetration (simply getting under the skin) and absorption (breaking into the bloodstream). Penetration is not necessarily problematic because once a substance enters the body, it may be turned into another chemical or metabolized by the body.
The other alternative is that it accumulates. This is where things get tricky because when it comes to toxicity often the dose is the deciding factor (many otherwise non-harmful substances can become toxic at high concentrations). Our bodies have a theoretical threshold at which the accumulated amount of a substance becomes unsafe. This point is different for each person.
So the answer to the question, “Does our body absorb what we put on our skin” is “yes and no”. Some substances definitely do make it through — especially if aides like emulsifiers increase absorption rates, but it is hard to provide a generally applicable formula. Governmental bodies like the FDA limit the amount of ingredients that can be used to increase absorption rates, but as discussed here, FDA regulations are not always full-proof.
So what should you avoid?
As mentioned above, exposure is the key factor to consider when it comes to chemicals. For example, something you splash onto your face briefly will have a different effect on your skin compared to a lotion that you put on your body and allow to soak in all day. That is to say, be extra careful with products that are exposed to a large surface area (e.g. body creams, bath salts). Shampoos make it onto that list as well as the foamy residue eventually runs off onto your entire body.
Parabens and formaldehyde are some of the most worrying chemicals you would do well to avoid. Parabens are preservatives which have been shown to be estrogen mimics. These can have adverse effects on your hormonal household, so much so that many of them have been banned by the EU. Formaldehyde has been linked to cancer in a high publicity lawsuit against the multinational cosmetics manufacturer, Johnson & Johnson. Both of these could get into your bloodstream through your shampoo, so it is advisable to get a plant-based alternative for some peace of mind.