In this blog post I’d like to examine a hotly discussed topic in the world of skincare – can cosmetics be absorbed into your bloodstream?
In one corner we’ve got a group of people who claim that the skin is such an effective barrier that hardly anything can pass through into the deeper layers of the skin, let alone the bloodstream. In the other corner, the natural/holistic world regularly spreads snippets around the internet about 60% of chemicals in cosmetics ending up in the bloodstream or 5 pounds of cosmetics being absorbed by our bodies every year or it taking 26 seconds for cosmetics to be absorbed into the bloodstream. What’s true?
A Brief Lesson in Skin Anatomy
Let’s start by looking at a diagram of the skin. The skin consists of several layers, which are grouped into the epidermis (the top layer), the dermis (next layer down) and the hypodermis (bottom layer of the skin).
The epidermis is the first barrier between us and the world, the dermis cushions us from any blows the world has to deal us and the hypodermis is mainly used for fat storage and contains blood vessels. All three of these layers in turn are made up out of other layers. The epidermis alone consists of another 4-5 layers despite it only being between 0.5 – 1.5mm thick depending on where on the body you measure it.
These layers in turn are made up out of human cells which are very complex structures with lots of barriers preventing chemicals from moving in, around and out of them easily.
What I’m trying to show you here is that any chemical that’s going to make it from outside of our bodies all the way into our bloodstream has a long way to go. It’s going to be a brutal adventure en-route and many will not survive.
Oil and Water do not mix
The outer layer of the epidermis, the stratum corneum, is lipophilic (oil-loving) and hydrophobic (water-hating) which is why we don’t turn into huge inflated bags of water every time it rains or we have a shower. Oils penetrate into this top layer and generally don’t make it that much further. The layers deeper down in the epidermis start to change in chemical composition and contain more water, making it harder for oil to penetrate further into the skin because oil and water do not mix.
Oil traps water beneath it and prevents the loss of water through evaporation thereby making your skin feel softer and smoother. Mature skin produces less oil as it ages so will benefit from the barrier effects provided by a good facial oil if applied at least once a day. The same goes for dry skin.
But will most carrier oils make it into your bloodstream when applied to the skin? It’s unlikely. There’s too much water in our bodies stopping it from getting too far in and too many skin layers trying to stand in its way.
Remember how to make mayonnaise?
That’s why the cosmetics industry has found a handy little trick for getting past those pesky skin defenders – emulsification: the process of blending oil with water to make an emulsion. Much like you effectively blend oil and water-based ingredients to make mayonnaise using an egg yolk to bind them together, all of your lotions and creams are generally a blend of oil and water with an emulsifier.
This is the reason that most people prefer to apply a lotion to their skin instead of a thick cream – they prefer the feel of a lotion quickly absorbing, rather than a thick oily cream sitting on the outer layers of the skin for a long period of time.
Cosmetic scientists can trap the anti-ageing compounds which you want to get deeper in the skin in a blend of oil and water. If a product is ‘amphiphilic’ (both oil- and water-loving) it can make it deeper into the layers of the skin (Förster et al., 2009) although this really does depend on the chemical in question and how it reacts with its ‘vehicle’ and the skin (Cal, 2006).
All of a sudden, those blood vessels are looking tantalisingly closer. Nonetheless, that still doesn’t mean that your lotions, creams and serums are being absorbed into your bloodstream. Absorption still depends on molecule size, chemical solubility, the ‘vehicle’ in which it is transported (i.e. your beauty product!) and whether or not the chemical reacts with the enzymes in your skin.
Your skin fights back… doesn’t it?
Your skin is an amazing organ and it’s filled with all sorts of protective measures that fight back. It’s an epic battle at times and many chemicals will simply not make it. Some chemicals will never get that far in the first place because their molecules are too big and they can’t pass into the skin. Others are retained on the skin’s surface because they bind with other chemicals or even bind with the skin itself.
However, for those that do make it into the skin, they may encounter enzymes that can break down or inactivate toxic chemicals. For some chemicals, such as some of the phthalic acid esters, the enzyme activity is so efficient that the chemical is completely metabolised during skin absorption (Hotchkiss, 1994).
However, there are also enzymes in skin that may activate chemicals or make them more toxic. In 1775, an English doctor named Percivall Pott noticed an increase in scrotal cancer in chimney sweeps due to skin contact with the polycyclic aromatic hydrocarbons in soot. More recently, scientists have established that the hydrocarbons themselves are harmless, but that specific enzymes in the skin convert them into reactive compounds that can damage cellular DNA and so cause cancer.
We now know that enzymes in the skin can activate and inactivate many drugs and foreign compounds as well as the body’s own natural chemicals such as hormones, steroids and inflammatory mediators. The activities of these skin enzymes, however, may vary greatly between individuals and with age (Hotchkiss, 1994).
In other words, our skin protects us from exposure to certain chemicals while actually intensifying the effects of others.
We’re all individuals
And if that all wasn’t complicated enough, all of us have different skin types depending on our age, skin colour and environment. Even the seasons affect the ability of our skin to deal with different chemicals. Even the specific activity we’re doing can affect how chemicals penetrate our skin and how they are then further absorbed.
For instance, having a massage with lots of essential oils may increase their penetration into the skin as the massage itself increases blood flow to certain areas of the body. Although many essential oils contain lots of wonderful chemical compounds that have anti-inflammatory and skin regenerating properties, some also contain skin sensitisers and allergens.
People with skin disorders such as dermatitis or very dry skin may also be sensitive to certain chemicals penetrating deeper into the layers of their skin. Their skin’s barrier properties can be compromised which means that the defences normally inherent in our skin are not functioning as normal.
Penetration rates of chemicals into the skin are also affected by the body part they’re applied to. The skin on the soles of our feet is very thick, whereas the skin of our eyelids is extremely thin. Absorption rates on our face and scalp are 5-10 times higher than on other parts of our body (Hotchkiss, 1994).
Some chemicals enjoy hanging around
Certain chemical compounds actually remain in the skin and act as a reservoir, being released (or not) at a later time. The design of particular medicines takes this into account – for example, salicylic acid was found to be excreted in urine more slowly when applied on the skin than when injected (WHO, 2006). Designers of pharmaceuticals can take this into consideration when designing drugs that would work better with a slow release system.
And this is an important point to understand – the people who design your beauty products are specifically trying to keep certain chemical ingredients in the upper layers of the skin. Cosmetic chemists do not want skincare products to enter your bloodstream because then they become drugs. After all, cosmetics are there to provide benefits to the appearance of the skin.
Think about sunscreens – you need UV absorbing ingredients to stay on the skin surface in order for them to have any benefit. Or what about skin lighteners – certain ingredients will need to make it all the way down to the hypodermis to inhibit the enzyme responsible for melanin production, whereas others will need to stay on the skin’s surface in order to have a bleaching effect. Those wonderful antioxidants and anti-ageing ingredients? They need to stay in the epidermis and dermis for them to do what they say they’ll do.
Nonetheless, that doesn’t mean that cosmetic chemists know everything. The skin is a complex organ and the cosmetics industry uses thousands of different chemicals. Take perfume or aftershave for instance – these common beauty products generally contain ethanol which has actually been found to increase absorption. Research has found that for certain compounds found in fragrance ingredients, absorption levels can be high (Hotchkiss, 1994).
Can you absorb a pizza through your skin?
Our skin is an amazingly effective barrier. Don’t ever forget that, particularly when you read lots of scary statistics. As one cosmetic chemist said on an online forum – “Imagine putting a piece of pizza on your skin. How much of that do you think will be absorbed?“. This statement is of course slightly facetious but I can understand why certain scientists get exasperated when they read scare-mongering articles about us absorbing everything we put on our skin.
Nonetheless, consumers are concerned and rightfully so. Personal care products over the last century have contained all sorts of ingredients, many beneficial, many superfluous and many downright nasty. There’s a reason that regulators have banned certain chemicals from being allowed in our personal care products.
It’s clear that there are ways and means for certain chemicals to make it all the way into our bloodstream. Our skin is not an impermeable sheet of plastic. Stuff gets in and makes it down into the bottom layer of the skin where the blood vessels are. Luckily even then the body has defence mechanisms which can kick into action, depending on what’s entered your body in the first place. That doesn’t mean that all chemicals are neutralised though and some will undoubtedly make it into your bloodstream.
It’s probably best to ask yourself whether you want some of these chemical compounds there in the first place. They may be there in minute quantities but that doesn’t make them inherently risk-free. My personal preference has always gone out to beneficial plant-derived skincare. If you know what you are using is good for you or even edible, you are generally going to be less concerned about applying your beauty products. And in the case of babies and young infants, I think you should avoid cosmetics altogether if possible (see my previous article on ‘Do babies need cosmetics?‘).
The Final Verdict
So in response to that question I asked at the beginning of this blog post, I think the answer lies somewhere in the middle. Those chemists who say that our skin holds back the tide are generally right – our body’s largest organ protects us from the daily onslaught and can stop certain chemicals from getting into our bodies.
On the other hand, the natural/holistic movement has a point – while our skin isn’t a sponge, it’s certainly taking in some ingredients that we apply to our bodies and transporting them further down into the body where they may or may not make it into the bloodstream.
But one thing is absolutely clear: it is impossible to put a figure on this absorption rate and it is impossible to estimate how much ends up in our bloodstream. Every person is different and every chemical is different. It is always good to question what you put on your skin but your body’s response will be individual.
My advice to you? Read your labels, understand what you’re putting on your skin and consider a gentler alternative if you want or need one. There’s nothing wrong with being cautious. If you don’t want to use certain ingredients, then cosmetic chemists need to look for alternatives. Ultimately, the customer is in charge.
What do you think? Are you concerned about chemicals from your personal care products making it into your body? Leave a comment below!
References and Further Reading
Cal, K. 2006. Skin penetration of terpenes from essential oils and topical vehicles. Planta Med. 2006 Mar;72(4):311-6.
Förster, M., Bolzinger, M., Fessi, H., Briançon, S. 2009. Topical delivery of cosmetics and drugs. Molecular aspects of percutaneous absorption and delivery. Eur J. Dermatol. 2009; 19 (4): 309-323.
Hotchkiss, S. 1994. How thin is your skin?: Skin seemed like such a good way of keeping the outside world at bay until toxicologists started to worry about the harmful chemicals that breach the barrier. New Scientist.
Personal Care Truth, 2011 – The Impermeable Facts of Skin Penetration and Absorption http://personalcaretruth.com/2011/01/the-impermeable-facts-of-skin-penetration-and-absorption/
WHO (World Health Organization), 2006. Dermal Absorption.http://www.who.int/ipcs/features/2006/ehc235/en/