And it doesn't matter how many times we try to dismantle it, it keeps coming back! But when it's shared by doctors turned skincare professionals who apparently forgot bio 101, it's just plain unforgivable.
The fact of the matter is, that statement is not true, or as we would say in 2022, fake news. (Do we still say that?)
Permeability of the skin
The skin, the largest organ in the human body, serves as a barrier, and it does an amazing job at it. It keeps your insides — muscles, veins, tendons, bones, organs and everything else — from spilling out, as well as keeping most of what surrounds us from getting in, including water, soil, dust, germs, viruses, bacteria and more. If that wasn't the case, we would become shampoo, soap and water balloons after every shower we took. That's a funny visualization isn't it?
Skin doesn't absorb UP TO 60% of what you put on it. That's a flat out lie.
This UP TO 60% is not a defensible ballpark either, nor an exact measure, it's a very inflated and non-precise estimate if you will, because for whatever reason people need to have a number tied to everything. It is best understood as a viral statistic: a number that sounds authoritative, but does not map to how dermal absorption is evaluated in dermatology, toxicology, or regulatory risk assessment. Regulators use compound-specific dermal absorption values (often derived from in vitro/in vivo studies) because the range can vary dramatically from one substance to another.
But this non-precise inflated number is dependent on many factors including but not limited to, what it is that our skin comes in contact with, in what concentrations, the age of the individual, their weight, pH of the chemical, what part of the body the chemical comes in contact with — as not all our skin has the same absorption ability —, the temperature of the body and the temperature of the compound at the moment of contact, the overall health of the person, the physical health of the skin, and the size of the molecules, among many other factors.
The thickness of the skin, the number of cell layers, cell size of the epidermis and the stratum corneum, and the distribution of hair follicles affect skin permeability greatly. As a rule of thumb, the thinner the skin, the higher its absorption rate.
By Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10x.JPG: KilbadCropped and labeled by Fama Clamosa (talk) and Mikael Häggström, respectively - Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10x.JPG (Public Domain)Scale at lower left was created from the an estimation of mean epidermal cell nuclei of 8.6 μm according to the following study:(2011). "Automated identification of epidermal keratinocytes in reflectance confocal microscopy". Journal of Biomedical Optics 16 (3): 030502. DOI:10.1117/1.3552639. ISSN 10833668., Public Domain, https://commons.wikimedia.org/w/index.php?curid=10759481
By Mikael Häggström, based on work by Wbensmith - File:WVSOM Meissner's corpuslce.JPG by Wbensmith.Layers were drawn according to image at Home Page of Deborah S. Dempsey, Department of Biological Sciences Northern Kentucky University > V. SKIN > 2 LAYERS ([1]), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10759398
The reason this 60% number claim fails is that it treats “skin absorption” as a single, uniform event. In reality, toxicology distinguishes between (a) material that remains on the surface, (b) material that enters or binds within the stratum corneum, (c) material that reaches viable epidermis/dermis, and (d) material that becomes systemically available. Those are different endpoints, and only the last one supports “goes into the body” claims.
If 60% was an exact measurement, then imagine the size your body would become just by swimming in a pool or the ocean. 60% of the water in that pool or beach would be inside you in no time. Instant human water balloons. Yet that never in the history of ever has happened.
Water for example cannot penetrate the skin from the outside in beyond the stratum corneum. This is because the skin is good at what it does, and because the stratified squamous epithelium a.k.a. stratum corneum, is keratinized, making it impermeable and waterproof. Water will get into the cells of the outer layer of the epidermis, the stratum corneum, swelling them up, but won't go in any further, which is why sitting in a pool of water for a while will get you looking all wrinkled up like a prune, instead of a human water balloon.
Our skin is permeable up to a point, or impermeable up to a point, however you want to see it. (1, 2)
Some chemicals do make it through without a problem, while some others do not, and there is a basic reason why, the size of their molecules.
Size Matters. But not Always.
Let me introduce you to the 500 Dalton rule, a useful heuristic in dermatology and transdermal science. The rule states in general, molecules above ~500 Da rarely penetrate the stratum corneum in meaningful amounts, which helps explain why many contact allergens and many transdermal drugs are on the smaller side <500 Da. But molecular weight alone is not enough: partitioning (lipophilicity), polarity/ionization, vehicle effects, dose, temperature, and skin condition can dominate real-world penetration. (3)
Water for example, has a molecular weight of 18.01528 g/mol = 18.01528 Dalton. Glycerin on the other hand has a molecular weight of 92.09 Dalton. In theory according to that rule water and glycerin should be able to pass through the skin just fine, and yet they don't. That's because, as I've mentioned above, the skin on top is impermeable and waterproof.
Both water and glycerin molecular weights are very small, and in theory they would go through the skin without any problem, but they are also highly polar and do not readily partition through the lipid-rich pathway of the stratum corneum. They primarily act by hydrating the stratum corneum (humectancy), specifically swelling up dead skin cells, not by entering the bloodstream in any meaningful fraction under normal use. However the chemicals in those substances could potentially make it through while leaving everything else out.
Depending on the size of the molecules, pH, polarity, and a load of other factors, certain substances will sit atop the skin, within the outer layer of the skin, or permeate all the way through in some instances almost intact and unchanged.
In cosmetics in particular most ingredients cannot penetrate the skin, simply because their molecular sizes are too large or their polarity is not correct. Some active ingredients designed to be transported into the skin or absorbed by the skin, are either incorporated into the skin's connective tissue, where they do their magic as we say, or are metabolized a.k.a. broken down by our skin and body. What is needed remaining in the layers of the skin, and the excess going into the bloodstream and discarded by the organs in charge of removing toxins from our body (kidneys, liver, and colon - no, your skin and your lymphatic system are not detox organs).
Unfortunately not all ingredients do that, and that's where cosmetic chemists must be very careful. Cosmetic chemists, for the most part, avoid unintentional dermal penetration of active ingredients at all cost. At least most of us do. In a desperate race to achieve the so elusive perpetually youthful appearance, some formulators forget our scope is to improve the appearance of the skin without damaging or affecting it negatively.
A quick technical clarification: nanoparticles are not “small molecules.” The 500 Dalton rule refers to molecular weight, while nanoparticles are typically discussed by particle size (nanometers) and behave very differently. In most cosmetic contexts, concerns about nanoparticles are evaluated case-by-case (material, coating, solubility, aggregation, application site, and whether the skin is intact). It’s not accurate to equate “nanoparticle” with “<500 Da,” and doing so can be challenged.
Of the many ingredients in cosmetics in vogue in recent years, colloidal precious and semi-precious metals, such as gold, silver, titanium and the like, with quite bogus, narrow and unscientific (pseudo scientific) claims, are being used in cosmetics preparations, even against current regulations at levels not safe for regular or daily use. These powdery metals, taunted as the next best thing in cosmetics, can penetrate the skin without any effort remaining seemingly unchanged, for the most part, and that's a problem.
Proponents of these precious and semi-precious metals in skincare are focusing solely on the benefits these metals allegedly pose to the skin, and I say allegedly because the results are not conclusive, without taking into consideration the possible negative side effects.
Because the human body has absolutely no use for these metals, opposite to iron and copper for example, which the body needs in relatively very small quantities to properly function, silver, gold and titanium have the potential for being detrimental to our overall health and well-being, as discussed in quite numerous studies conducted in vivo and in vitro.
Just because it shines doesn't mean it's good for you.
If you don't fancy a smurf like silvery blue skin color with lots of health issues as side effects, you may want to stir away from cosmetics containing colloidal silver. If you don't want to potentially suffer from kidney, liver, intestine and spleen damage, you may want to avoid cosmetics with colloidal gold instead. (4, 5)
It's a good practice to be aware of what we put on our skin, just as much as what we eat, drink and breathe. Knowing what ingredients to look out for, their benefits or possible negative effects, and which ones we should completely avoid is important for our overall well-being. But assuming everything we rub on our skin will be absorbed is not a reality, but a baseless myth created just for marketing purposes, particularly in the "natural skincare industry".
Awareness shouldn't be translated into fearmongering, but conscious knowledge so we can ALL make informed decisions.
But where is the 60% coming from?
The short answer: there is no credible primary source for “skin absorbs 60% of what you put on it.” When you look for a traceable toxicology papers, dermatology textbooks, or regulatory documents, the 60% figure does not appear anywhere.
How the number likely got invented has nothing to do with reality or science, as there isn't one source for it but a bundle of data turned into a scary percentage.
What does exist is legitimate science on dermal absorption, and that science is almost the opposite of what proponents of this fallacy imply: absorption is substance-specific and must be measured under defined conditions.
1) A mash-up of real concepts, turned into a single scary percent
There is legitimate science on dermal absorption. But what many fail to understand is that dermal absorption depends on the chemical, the molecule and the context: molecular weight, lipophilicity, formulation/vehicle, dose, exposure time, skin site, integrity (e.g., irritation, eczema), occlusion, temperature, and more. Because of this variability, regulators explicitly treat "% dermal absorption" as something that has meaning only for a given substance under a very defined exposure scenario and conditions, not as a single “always true” constant percentage.
2) Confusion between “penetration into skin” vs “systemic absorption”
A common rhetorical trick in the "wellness" and “clean beauty” content is to blur context:
- penetration (into stratum corneum / viable epidermis)
vs - absorption (reaching systemic circulation)
Those are not the same endpoint, but the “60%” claim is usually framed as if most topicals reach the bloodstream — which is biologically implausible as a general rule.
Most topical ingredients and actives used in cosmetics, under normal cosmetic use, are not systemically absorbed at high fractions, and many mostly remain on the surface or within the outer layers. Regulatory guidance and dermal absorption test methods explicitly distinguish these endpoints.
3) This myth often travels with a second one: “26 seconds to bloodstream”
The “60%” claim commonly appears paired with “in 26 seconds,” which is a tell: both have the fingerprint of viral infographic statistics, not reproducible research. Even mainstream lifestyle coverage that mentions these numbers typically notes they are not scientifically supported. You can see these paired claims repeated across marketing and social content.
4) “Authority laundering” through vague attributions
You’ll often see the number posted by itself as a stand alone fact, especially from estheticians and skincare gurus, attributed to unnamed “studies” or “scientists,” or to institutions without a citable publication. That style of sourcing makes a claim look authoritative while remaining non-verifiable. Example: claims attributed to the “Health Science Institute” circulate widely, but without a primary, verifiable publication tied to the specific 60% figure.
5) Why it persists (even among professionals)
- It’s simple (one number), memorable, sounds previse and fear-anchored.
- It’s useful for “clean” positioning and for selling “safer” alternatives.
- The real explanation (permeation science) is nuanced, and because nuance spreads poorly, fearmongering language is used as an absolute truth. Example "our chemical free skincare..."
Skin is a barrier organ, highly effective at protecting us, our muscles, bones and internal organs from external intrusions. Systemic absorption from cosmetics is not "60% by default."
Some molecules can absorb meaningfully under specific conditions, and that is why risk assessment uses compound-specific dermal absorption data, not universal percentages.
