Once upon a time, probably at some point in the past 200 years, a group of aliens landed on earth, undetected, from another planet in a distant galaxy. These aliens looked identical to humans, and they were able to disperse and interbreed with humans. The only difference between these aliens and humans was that the aliens’ skin was porous, like a sponge. The descendants of these aliens live amongst us but, as skin porosity is a dominant gene, they still retain this characteristic.

This is the only reason I can find to explain the number of people who insist that everything that is put on the skin in absorbed.

I am sure you’ve seen the claims:

“The skin absorbs everything you put on it”

“You absorb up to 60% of everything you put on your skin”

“Your skin is like a sponge”

. . . and various other similar claims.

The claim is almost always preceded by “skin is the largest organ in the body”, as though this implies that this is a little-known fact and the writer has a unique insight into skin biology and is, therefore, highly qualified to make claims about skin absorption.

I have reproduced below a classic exchange on this very subject:

Marilyn:

Our skin is a sponge and it absorbs everything we put on it. When it’s absorbed, it gets into the bloodstream.
If you doubt that your skin is so absorbent, have someone rub the cut side of a clove of garlic on the sole of your foot and within seconds you will TASTE the garlic….NOT just smell it.

Dene:

@ Marilyn D – if your skin is a sponge, can you please explain to me how it is possible for us to have a bath, or go swimming? Where do you get your information from?

Marilyn:

Dene G…you seem hell-bent on defending the use of chemicals so I assume you have an agenda.
It seems that you are the one in need of some research. By the way…do the garlic test and then tell me your skin doesn’t absorb what you put on it. One need not be a chemist to taste the garlic. You call me names for saying our skin is a sponge and then ask how we can bathe….DUH…even a sponge has a capacity beyond which nothing can be absorbed. Talk about ludicrous…just to prove your point!!

Dene:

The garlic example is a classic case of a little information going a long way, and being totally misunderstood! Smell is closely related to taste. If you hold your nose whilst drinking wine, for example, you cannot smell the bouquet. [Whilst I am reproducing the actual text used, this statement is actually totally wrong, and I had meant to say that you can’t taste the wine – no-one in the discussion picked up on this!] When garlic is applied to the foot, the smell is picked up by the nose and is “tasted”. If it were due to skin absorption, it would have to be transported in the blood – which would require more than a few seconds. [Additionally, I am not convinced that the garlic – or any other substance can reach the taste buds after being absorbed through the skin, but I would need confirmation of this by someone who actually knows!]

You clearly have no understanding of the skin, by sticking to your “sponge” analogy. You seem to be implying that our bodies are “full” of water. Why do we bother to urinate when we have too much water in our bodies – why don’t we just let it drip out through our skin? Check out the “human skin” entry on Wikipedia – ask any doctor or dermatologist – they will all tell you that skin is a barrier, and only a small % of what goes on the skin is actually absorbed.

Marilyn:

Dene…then I guess there is no such thing as transdermal medication…or pain patches or nicotine patches. According to you, they wouldn’t work. You had best get in touch with the pharmaceutical companies and let them know that you know better than they do. Regarding the absorbency of skin…if one drop of tea tree oil on my fingertip can trigger a severe asthma attack within 5 minutes, then I would deduce that we DO absorb a LOT through our skin.
Why take chances with toxic products? I’ve found a way to make my own products using ingredients that are safe.

Dene:

@ Marilyn – at no point have I stated that NO substances are absorbed through the skin. I have simply said your sponge analogy is totally wrong. I have also explained why some people think that garlic is rapidly absorbed. As an asthma sufferer, I would have expected you to know that this is a lung condition. Tea tree oil has a very powerful odour (I know – I’ve worked with it myself) – it is the vapour that triggers your asthma. Of course transdermal patches work on the basis of skin absorption, but a lot of work goes into developing them, simply because the skin is a difficult barrier to breach. SOME substances CAN be absorbed, but by no means all are. You seem to only deal in absolutes – life is not like that.

Marilyn:

Dene G…you can call me arrogant or ignorant or whatever floats your boat, but don’t assume that I don’t know whether I inhaled tea tree oil fumes or had skin contact with it. ANY product containing even the smallest amount of tea tree oil will trigger my asthma attacks. If you knew anything about chemical sensitivities and allergies you would know that those of us with those conditions often have a HYPER-ACUTE sense of smell and would know if we smelled something.
Your stubborn stance in defense of chemicals simply means that you are indeed in the right profession…the one that doesn’t care whether the chemicals that give us lather and fragrance and color in our products also give us cancer.
You are the problem. Sadly, too many scientists live by the credo of ‘if you can’t measure it, it doesn’t exist’. You’ve lost touch with humanity. Perhaps it’s all the over-exposure to chemicals in your workplace…dulling your senses!

Dene:

@ Marilyn – you seem to be willfully ignoring what I say – I am NOT defending ALL chemicals – only those wrongly attacked in this article. I do NOT defend the use of any chemical (natural or synthetic) if there is proof that its use is not safe. Your willingness to accuse those who don’t agree with you of being uncaring is disingenuous. Is it really the case that you, and people who agree with you have the sole right to be caring? I lost a good friend to cancer a few years ago, and it was almost certainly his exposure to one or two specific chemicals in the course of his work that were the cause. I care. I also care about getting things right, and telling the truth. You have no idea of the atmosphere in my workplace – how can you comment on it? I work from home! You have no facts to support your defence of this article – you resort to attempts to undermine my credibility instead. Why should anyone believe YOU?

Marilyn:

There was no further reply!

Note the use of only two (poor) “examples” to “prove” that skin absorbs everything! One further point that I did not get the opportunity to add in this discussion is that, if skin were a sponge, anyone who is dehydrated would only need to sit in a bath to cure the condition. Clearly, this is NOT the recommended treatment for dehydration.

I have heavily edited these comments, believe it or not, to keep it more relevant to the subject in hand, although I have left in some of the more “personal attack” comments as an example of how these discussions stray into other territory, especially when one of the participants is speaking from a position of ignorance of the science. For anyone wishing to see the entire discussion – but be warned, it’s not for the fainthearted, there are over 600 comments!

I have used these extracts from another discussion because they provide all the elements of the standard response (garlic on the foot being tasted, and tea tree oil) when anyone questions the misinformation about skin absorption, plus what I believe to be an accurate rebuttal. To further support my claims, I have quotes that I have requested from two eminent dermatologists specifically to use in these discussions:

“The skin possesses an outer layer which is a very impressive barrier. It is about one sixth the thickness of a piece of paper but stops us losing excessive water. This is because of its unique structure.

Absorption is variable depending on:
the skin site and its condition,
the properties of the active applied,
the product in which the active is applied.

For the great majority of materials the percent of dose absorbed is around 1-2%
For some it is less than 0.1%
For some, very few, it is 10-20%

The barrier properties of the skin and the resulting low absorption into the skin are a major problem in the topical treatment of skin conditions and diseases. The majority of compounds that have potential to affect the biology of the skin are rarely delivered in amounts to allow them to realise that potential. “

Jonathan Hadgraft DSc
Professor of Biophysical Chemistry

The School of Pharmacy

University of London

“The normal skin barrier provides protection for the body against the penetration of irritants and allergens from the environment and the loss of water out through the skin. Without this very effective skin barrier humans and other land animals would die from dehydration within a day”

Professor Michael J. Cork

Head of Academic Unit of Dermatology Research Dept. of Infection and Inflamation, Faculty of Medicine, The University of Sheffield

So many commentators quote that “up to 60% [sometimes higher % are quoted] of cosmetics are absorbed by the skin”. Many others wonder where this information came from.

I believe that this is the original source of that claim:

In vitro skin permeation and retention of parabens from cosmetic formulations

Auteur(s) / Author(s)

PEDERSEN S. (1) ; MARRA F. (1) ; NICOLI S. (1) ; SANTI P. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Dipartimento Farmaceutico. University of Parma, Parco Area delle Scienze, 43100 Parma, ITALIE

Résumé / Abstract

Parabens are antimicrobial agents widely used in foods, cosmetics and pharmaceutical products. Although non-mutagenic, non-teratogenic and non-carcinogenic, parabens can induce allergic contact dermatitis and posses estrogenic activity. The aim of this work was to assess the skin permeation and retention of methyl- (MP), ethyl- (EP) and propyl- (PP) paraben from three commercial cosmetic creams. The results obtained indicate that parabens are capable of permeating through and accumulating in the skin. The extent of penetration depends more on paraben characteristics (solubility, lipophilicity) than on the composition of the formulation. In particular, the percentage permeated across the skin was independent of the composition of the cream used and decreased in the order MP, EP and PP, in accordance with decreasing solubility. After 8 h of contact with the skin, 60% of MP, 40% of EP and 20% of PP were found across the skin. Concerning skin retention, the percentage remaining in the skin after 8 h depends on both paraben characteristics and on the composition of the formulation used. In conclusion, it appears that only the type of paraben, in particular its water solubility, affects skin penetration whereas the composition of the emulsion, which influences skin retention, plays a secondary role. Finally, excised rabbit ear skin can be considered as a good model for human skin for in vitro experiments.

Revue / Journal Title

International journal of cosmetic science ISSN 0142-5463 CODEN IJCMDW

Source / Source

2007, vol. 29, no5, pp. 361-367 [7 page(s) (article)] (20 ref.)

It is vital to note that the only mention of “60%” was for methylparaben. This single data point seems to have been wildly extrapolated to encapsulate ALL cosmetic ingredients. Clearly, this is an outrageous distortion of the findings of this study, and one can only speculate on how this has happened, but I suspect that, at some early point, it was a deliberate distortion by someone who needed to scare consumers.

[As an aside, especially considering that parabens were the substances under investigation, it is important to me that I add the following comments made on a blog where this information was being discussed: “According to your source (Pedersen), 60% of methylparaben is absorbed by the skin when applied in a cosmetic. I take issue with that study making the claim that excised rabbit skin is a useful model to mimic human skin. Parabens have been showed to be easily degraded by esterases in the skin (and in the blood), and excised rabbit skin will have no esterase activity as this ceases very soon after the demise of the animal. Therefore, both your statement and that of Pedersen et al are highly disputable, in terms of the reality of living human skin, particularly as a much more recent and more in-depth study (as yet unpublished) has claimed that parabens are barely absorbed through the skin – and this was an in vivo study and, therefore, significantly more relevant than Pedersen’s in vitro study.”]

In summary, there is NO basis for the claim that ALL cosmetic ingredients are absorbed by the skin. (There is also NO basis for the claim that skin is like a sponge – this is simply ridiculous.) Like many (most?) extreme claims (using ALL or NONE), it is not correct, and the truth lies somewhere in between the extremes. Clearly, SOME ingredients are absorbed to different extents, varying between very low and very high, and some are not absorbed at all. However, in some ways, the extent of skin absorption is irrelevant. If the substance is absorbed, metabolised and excreted without causing any measurable adverse effect, then there is no cause for concern. Unfortunately, the “skin is a sponge” story is used to imply that it is automatically dangerous if the ingredient does enter the skin. This is pure scaremongering.

Author

Dene Godfrey has been involved with preservatives for cosmetics since 1981, from both technical and commercial angles and has a degree in chemistry. Dene worked for one of the largest manufacturers of parabens from 1992 – 2002, and currently works for a UK company involved in the distribution of ingredients for cosmetics, health care and food. The Boots Company, 1973 – 92, Dene spent 11 years working with bronopol, although he was also involved in the initial development of Myavert C, now known as Biovert – a well-known “non-preservative”. Latterly was responsible (as Technical Manager) for the operation of the Formulation Laboratory and the Microbiology Laboratory. As Technical Manager when at Nipa Laboratories, Dene was responsible for development and sales of new preservative products, mainly into personal care. Developed the Nipaguard range of preservatives and co-patented a preservative system based on phenoxyethanol and IPBC. In 2002, Dene founded MGS MicroPure (as Technical & Sales Director) to compete with the giants of preservation, establishing the Paratexin brand name in the UK and several other markets (EU/ global). MGS MicroPure ceased trading in 2005. Since 2005, Dene has been employed by a major UK distributor of personal care ingredients, with his focus primarily on preservation systems. Dene’s articles are based solely on his personal opinions, observations and research, and are not intended to represent any official position of the part of his employer. Dene obtained a BSc (Hons) in Chemistry from the Open University in 1996. He also obtained the Professional Certificate in Management from the Open University in 1997. He has been an active member of the UK Society of Cosmetic Scientists since 1992, and has served 4 terms on the SCS Council, and is involved with the SCS Social Committee from 1993 to date; from 2004 – 7 as Social Secretary. Dene has presented papers at many SCS meetings and was President of the SCS (2009/10)

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