Skin penetration of Ascorbic Acid

Today I wanted to look at a research paper primarily led by Dr. Sheldon R. Pinnell. He is one of the founders of Skinceuticals and contributed much of the early research on the use of Vitamin C as ascorbic acid on skin. He and his group also discovered the synergistic effect of Vitamin C, Vitamin E, and Ferulic acid – which is commonly used in many products on the market today.

The data from this paper is often quoted in marketing material for Vitamin C serums, but one extremely important piece of information is often left out – the data was collected from pigs, white Yorkshire pigs to be exact.

Many people also have ethical concerns when it comes to the use of animals in cosmetic research. Synthetic and lab grown human skin equivalents are being researched and tested which will one day replace the use of animal as well as human testing in cosmetics.

It should be clear that human skin and pig skin are not the same, but they do have similar properties which is why it is often used in experiments. However, one should never assume that data from a pig can be assumed to be the same for a human. The movement and deposition of chemicals often differs between human and pig skin.

From my searches, I haven’t been able to find similar research performed on humans. This paper in particular has led to some of the often quoted “rules” about ascorbic acid.

“Ascorbic acid must have a pH below 3.5 for effective penetration.”

Pinnell and his group tested a 15% ascorbic acid solution adjusted to different pHs ranging from 2 to 5. The 15% ascorbic acid solutions also contained 2% zinc sulfate, 0.5% bioflavonoids, 1% hyaluronic acid, and 0.1% citrate.

While the control situation wasn’t described it’s likely either the vehicle (product without the ascorbic acid) or a water solution was applied to the skin. The control measurement shows that there is some inherent levels of ascorbic acid already present in the skin from the diet.

The test solutions were applied to the pig skin using a Hill Top Chamber. A Hill Top Chamber is a small and round disk which is placed on the surface of the skin, the product is placed in the chamber or a piece of fabric is soaked in the testing material, and the entire chamber is then sealed. This prevents loss of product from evaporation and is a common method of performing occlusive test patches.

The ascorbic acid solutions at pH 2.5, 3.0, 3.5, 4.0, and 5.0 were performed on three pigs, however the control, pH 2, and 4.5 were only performed on two pigs.

The Hill Top Chamber was soaked with 0.2 mL of the ascorbic acid solution then sealed for 24 hours. After this period of occlusion, the skin washed then stripped of the stratum corneum and then small pieces of the skin was removed and tested for ascorbic acid content.

As you can see from the data, the amount of ascorbic acid found in the skin was much higher in ascorbic acid solutions at pH 3.5, 3.0, 2.5, and 2.0. The researchers theorize that it is due to the pKa of ascorbic acid which is 4.2. When the pH of a solution containing ascorbic acid is lower than its pKa more of the ascorbic acid will be protonated. Protonated ascorbic acid is neutrally charged which may allow it to enter the skin more easily.

It’s important to notice the error bars on the amount of ascorbic acid absorbed at pH 2.0. There is considerable deviation from the mean in the results even though it was only tested on 2 subjects. More test subjects would provide a clearer idea of how much ascorbic acid would penetrate at pH 2 on an average population of pigs.

Statistical differences also weren’t calculated between the data points, for example it’s difficult to tell from the way that the data is presented if there is a change in ascorbic acid content between the control, pH 4.0, 4.5, and 5.0 – even if they look different on the graph. Likewise, it’s difficult to tell if there is an increase in ascorbic acid penetration between pH 3.0 and pH 2.5 – despite the trend with pH 2.0 pushing you towards that inference. It’s likely that there is a statistically significant difference between absorption between pH 3.5 and 3.0, but a larger study would provide us  with more confident answers.

So based on this data, many further studies and brands have assumed that a pH below 3.5 results in considerable more skin penetration of ascorbic acid on humans – despite these results being performed on pigs, and relative low strength of the study. If the reason why ascorbic acid is more easily absorbed into the skin is due to the pKa then this would likely hold true for humans as well.

This assumption is often presented as fact, which is misleading. It also doesn’t take into account other factors present in a cosmetic product, such as penetration enhancers. Encapsulation, surfactants, and solvents could increase (or decrease) the amount of ascorbic acid absorbed into the skin regardless of the product’s pH.

In this experiment, the stratum corneum was removed before measurements of ascorbic acid to test for deep penetration of ascorbic acid. It’s possible that some of the benefits conferred by topical application of ascorbic acid aren’t facilitated by deep penetration, the antioxidant and photoprotective effect of ascorbic acid may still occur when it is present in or on the stratum corneum. Other benefits like reduction of hyperpigmentation and an increase in collagen production are likely dependent on penetration past the stratum corneum.

Unfortunately I haven’t been able to find further studies on humans or otherwise to provide answers to these questions.

“Ascorbic acid serums must be at least 10% to be effective”

After the first experiment of testing 15% ascorbic acid with different pHs, Pinnell and his group tested how concentration of ascorbic acid affects skin penetration. This time they tested 7 ascorbic acid solutions with varying concentrations all at pH 3.2. The concentrations of the rest of the formulation are assumed to be the same as the previous experiment.

The ascorbic acid solutions were applied in the same manner, with a Hill Top Chamber for 24 hours, followed by washing, stripping, and then assessment.

The maximum amount of ascorbic acid penetration was seen when 20% ascorbic acid at pH 3.2 was used.

All concentrations were tested on 3 pigs, and there is quite a bit of deviation from mean between absorption among the 3 pigs tested. This makes it difficult to assess the true difference in absorption between a 10% and 15% ascorbic acid, and a 15% and 20% ascorbic acid.

Absorption also seemed to peak at 20%, the 25% ascorbic acid solution penetrated less than the 20%, and the 30% even less so. The researchers did not explore or hypothesize on why this occured, and I’ve been unable to find an answer in any later research as well.

While 20% ascorbic acid certainly led to the greatest increase in levels of ascorbic acid, the 5% solution still increased ascorbic acid levels in the pig skin by about 6 fold.

It’s very important to remember that the way that this experiment was performed does not mimic the way that ascorbic acid solutions are often applied to the skin. With the Hill Top Chamber, the solvent (in this case water) is not allowed to evaporate – whereas when we apply it to the skin the solvent evaporates. What this means is that the kinetics of ascorbic acid penetration into the skin may not be the same.

For example, if half of the solvent of a 10% ascorbic acid solution evaporates, it is equivalent to a 20% ascorbic acid solution – the total amount of ascorbic acid by mass is the same, but the concentration has changed. This may mean that we could see a different maximum absorption by concentration in an experiment where the solvent was allowed to evaporate the way that it is often applied.

Human clinical trials with “low” ascorbic acid concentrations, 3% ascorbic acid cream and a 5% ascorbic acid cream, were able to show statistically significant improvements on measurements of photodamage and photoageing in their study groups.

Another thing many people hold on to is the concept that their products must be working at “maximum efficiency”, unfortunately this is unrealistic and there’s going to be variations in the amount of ascorbic acid that penetrates your skin with each application – even the amount that you apply to your skin will vary each time. This is why good cosmetic studies are performed over a longer period of time.

For example, if we look at the 20% concentration, the pig skin concentration of ascorbic acid increased to about 1100 pmol of ascorbic acid per mg of pig skin, which is about 0.19 μg ascorbic acid per mg of pig skin. 1.0 mg of a 20% ascorbic acid (w/w) contains about 1135589.37 pmol of ascorbic acid, if that helps give you a sense of the “efficiency”. In these experiments, 200 μL or 0.2 mL solution was used in total for each application, which contains about 227117874.1767 pmol of ascorbic acid if we assume density of the solution (w/w) is 1.

Higher concentrations of ascorbic acid may lead to more irritation (measured by skin redness or erythema), but I haven’t found any studies that looked at this specifically.

I’m going to end this post here, to be continued next week, where we’ll look at the data behind Vitamin C’s “reservoir” effect.

Source: Pinnell, S. R., Yang, H. , Omar, M. , Riviere, N. M., DeBuys, H. V., Walker, L. C., Wang, Y. and Levine, M. (2001), Topical L‐Ascorbic Acid: Percutaneous Absorption Studies. Dermatologic Surgery, 27: 137-142. DOI: 10.1046/j.1524-4725.2001.00264.x

Should you avoid sunscreens with Avobenzone?

I’ve received quite a few questions about the organic sunscreen chemical Avobenzone over the years and I wanted to shed some light on one of the most common concerns – its photodegradation in UV. These concerns are usually raised by websites that say things like, “Avobenzone degrades in the sun, resulting in the release of free radicals that may actually increase the risk for cancer.”

What these quotes often leave out is the context, which is important in understanding why Avobenzone is so commonly used in sunscreens and why it is effective.

Avobenzone or butyl methoxydibenzoyl methane is an organic sunscreen that absorbs in the UVA region and has global approval. Among the sunscreen chemicals available in the US it is the strongest and most effective UVA absorber. Avobenzone exists in two chemical forms when in solution, the enol form and the diketo (or keto) form.

When exposed to UV light some Avobenzone in the enol form can be changed into the keto form – however this is slowly reversed once Avobenzone is removed from UV light.

In its keto form Avobenzone is susceptible to photodegradation from UV light. The energy from UV light causes structural changes in the Avobenzone that can lead to breakdown products. In many cases, those breakdown products no longer effectively absorb UVA and UVB (some of them will absorb UVC). Some of these breakdown products are also thought to be irritants. The other concern is that some singlet oxygen can also be formed – a reactive oxygen species which can damage DNA and cells.

The above only relates to Avobenzone on its own though, the material that Avobenzone is dissolved into and other chemicals in the formula can change how easily Avobenzone photodegrades. Other modifications like encapsulating Avobenzone have also been tested, though the benefit is often reduced contact between Avobenzone and the skin – not photostability.

Photostabilizers generally work by absorbing energy from the Avobenzone before it becomes unstable and breaks and down. Effective photostabilizers will then be able to take this energy and dissipate it in safer forms, most often heat.

A company that produces Avobenzone, DSM Nutritional Products, performed a study testing different photostabilizers and their effect on Avobenzone’s phostability. The most commonly used and known photostabilizer of Avobenzone is the organic sunscreen chemical Octocrylene, but there are other photostabilizers that don’t act as sunscreens such as Polyester-8 and Polysilicone-15.

To perform the test, 4% Avobenzone and different photostabilizers were dissolved into a mixture of 70% ethanol, 15% caprylic/capric triglyceride, and 15% C12-15 alkyl benzoate. The solutions were placed on glass slides at a density of 2 mg/cm2 then exposed to 25 MED (Minimal Erythemal Dose, 1 MED defined by the US FDA as 200 Joules/Meter2) units of UV light. After exposure, the amount of Avobenzone remaining was determined.

What the researchers found was that the combination of 4% Avobenzone and 3-5% Octocrylene maintained 90% of the Avobenzone after 25 MEDs of UV light. Based on this, they tested different combinations of Octocrylene and other photostabilizers to see how well they stabilized Avobenzone.

They found that 3.6% Octocrylene with 4% Bis Ethylhexyloxyphenyl Methoxyphenol Triazine or 4% 4-Methylbenzylidene Camphor were able to completely stabilize the Avobenzone after 25 MED of UV.

There’s currently no global standard on photostability, different regions have their own standards. In the US as part of the Broad Spectrum test, sunscreens are pre-irradiated with 4 MED before testing.

Just like how some chemicals can increase the photostability of Avobenzone, others like Octinoxate (Octyl Methoxycinnamate) are known to speed up the photodegradation of Avobenzone. This paper is often misquoted to include Oxybenzone (2-Hydroxy-4-Methoxybenzophenone), often mischaracterized as not photostable, as a chemical that increases the photodegradation of Avobenzone, but it was included as an internal standard to allow comparison between samples – as it did not photodegrade in the experiment.

What matters when it comes to the protection offered by a sunscreen are the values and ratings determined from standardized tests like SPF, PPD, Broad Spectrum, etc and not the appearance of an ingredient on the INCI.

Basing assumptions on INCI is dangerous, as the only way to truly know is to test the products. An experiment on 6 different commercial sunscreens on their photostability highlights this. 4/6 of the organic sunscreens tested exhibited a decrease in photoprotection after UV exposure. Of the two photostable organic sunscreens one contained a combination of Avobenzone and 4-Methylbenzylidene Camphor and the other Octocrylene, Avobenzone, Mexoryl SX, and Titanium Dioxide. The one inorganic sunscreen tested was shown to be photostable after UV exposure.

Keep in mind, this study tested commercial sunscreens available in 2006, where photostability was a relatively newer concern for sunscreens and standards had not yet been defined. It was around this time that Neutrogena began marketing its Helioplex patent, a photostable combination of Avobenzone, Diethylhexyl 2,6-Naphthalate, and Oxybenzone. The Helioplex US patent was granted in 2002 and other patents for increasing photostability of Avobenzone are present as early as 1999, when the US FDA finalized the use of Avobenzone in sunscreens.

While we still do not have a global standard for photostability, the options for and knowledge to stabilize sunscreens has grown considerably. It also still very important to reapply your sunscreen throughout UV exposure, this compensates for any protection lost through photodegradation as well as physical changes in the film of sunscreen on the skin.

Source: C. Mendrok-Edinger, K. Smith, A Janssen, J. Vollhardt. The Quest for Avobenzone Stabilizers and Sunscreen Photostability, Cosmetics and Toiletries,

Everybody’s free to wear sunscreen

You’ve probably seen this photo of a man who received chronic UV exposure on the left side of his face over the course of 28 years working as a truck driver. While this shows the effect that UV has on the skin, what’s important to keep in mind is that windows only block UVB light whereas UVA is often passed through.

Chronic UVA exposure can result in thickening of the epidermis and stratum corneum, as well as destruction of elastic fibers.

Unfortunately, for those of us living in Canada, the US, and Australia the amount of UVA protection offered by sunscreens is only given in relative terms. The UVA circle logo, for example, let’s you know that the UVA protection is at least 1/3rd of the SPF protection of the sunscreen, but it’s not as informative as a UVA protection factor (UVAPF) or persistent pigmentation darkening (PPD) number. While the PA system used in some Asian countries is based on a PPD number, the data is compressed into categories.

My personal thought is that the UVA protection should be as close to the SPF protection as possible. These are the sunscreens that I personally recommend; based on UVA protection, how they feel and wear on the skin, and affordability. While there are many great sunscreens out there, many of them are too expensive for me and I end up “rationing” them – which is a no-no when it comes to sunscreen application.

Bioderma Photoderm MAX Spray SPF 50+ with UVAPF 33 is a large sized and affordable sunscreen with a moderately high UVAPF. It is a lipid based formula (Dicaprylyl Carbonate) which spreads easily and is not greasy on the skin. I recommend the larger 400 mL size which comes with a snap lock which makes it easy to travel with. I use this on face and body.

It prices out to about 10 US cents per mL.

Sunscreen filters in bold:

Aqua/water/eau, Dicaprylyl Carbonate, Octocrylene, Methylene Bis-benzotriazolyl Tetramethylbutylphenol [Nano], Butyl Methoxydibenzoylmethane, Bis-ethylhexyloxyphenol Methoxyphenyl Triazine, Cyclopentasiloxane, Methylpropanediol, Ectoin, Mannitol, Xylitol, Rhamnose, Fructooligosaccharides, Laminaria Ochroleuca Extract, Decyl Glucoside, C20-22 Alkyl Phosphate, C20-22 Alcohols, Xanthan Gum, Propylene Glycol, Citric Acid, Caprylic/capric Triglyceride, Sodium Hydroxide, Microcrystalline Cellulose, Pentylene Glycol, 1,2-Hexanediol, Caprylyl Glycol, Cellulose Gum, Disodium EDTA.

Ombrelle Ultra Light Advanced Weightless Body Lotion SPF 50 is another affordable sunscreen I recommend. Canada’s Ombrelle was acquired by L’Oreal which is why this product contains Mexoryl sunscreens, which are patented and used exclusively by L’Oreal companies. Because of regulations, the UVAPF or PPD is not able to be listed, but this does have the UVA circle logo. It contains 2% Mexoryl SX which is the stronger UVA absorber compared to Mexoryl XL. It is lightweight, dries quickly, affordable, and easily accessible for Canadians. While it is marketed as a body sunscreen, I use it on my face. It’s much lighter in texture compared to Ombrelle’s other sunscreens marketed for the face.

It prices out to about 12 US cents per mL.

Sunscreen filters in bold

Homosalate: 10%, Oxybenzone: 6%, Octisalate: 5%, Octocrylene: 5%, Avobenzone: 3%, Ecamsul (Mexoryl® SX): 2%. Others/Autres: Aqua, Cyclopentasiloxane, Alcohol Denat., Cyclohexasiloxane, Styrene/Acrylatescopolymer, Silica, Dicaprylyl Ether, PEG-30 Dipolyhydroxystearate, Dimethicone, Triethanolamine, Glycerin, Nylon-12 Polymethylsilsesquioxane, Dicaprylyl Carbonate, Tocopherol, Dodecene, Phenoxyethanol, PEG-8 Laurate, Poly C10-30 Alkyl Acrylate, Poloxamer 407, Caprylyl Glycol, Disteardimonium Hectorite,Disodium EDTA, Lauryl PEG

Sheer Zinc Face Dry-Touch Sunscreen Broad Spectrum SPF 50 is a newer sunscreen and contains only Zinc Oxide as its sunscreen filter. Be warned, this has a very strong whitecast and a thick silicone texture which can pill. I find it best to apply this to small areas of the skin while blending thoroughly.

The reason why I recommend this sunscreen, despite its drawbacks, is based on a presentation that Johnson & Johnson gave at the 2017 American Academy of Dermatology’s Annual meeting showing that their 21.6% Zinc Oxide sunscreen had a UVAPF of 30. Other inorganic sunscreens I’ve seen have only been able to reach a UVAPF of about 18-25.

While the Neutrogena Sheer Zinc was not explicitly named, the launch time and Zinc Oxide content of 21.6% suggests to me that this is the product described.

They compared its absorption spectrum, in vitro, with other common inorganic sunscreens and were able to show that it absorbed more UVA in comparison

I must say again how strong the white cast is, hopefully in the future they release tinted versions!

Based on the above chart it’s likely that the tinted Elta MD SPF 41 with 9.0% Zinc Oxide and 7.0% Titanium Dioxide has a UVAPF of around 28, I’ve not personally tried the product, but I do know it is popular. It prices out to about 35 US cents per mL.

The Neutrogena Sheer Zinc prices out to about 15 US Cents per mL.

Sunscreen filters are in bold

Zinc Oxide 21.6%. Others: Water, C12-15 Alkyl Benzoate, Styrene/acrylates Copolymer, Octyldodecyl Citrate Crosspolymer, Phenyl Trimethicone, Cetyl PEG/PPG-10/1 Dimethicone, Dimethicone, Polyhydroxystearic Acid, Glycerin, Ethyl Methicone, Cetyl Dimethicone, Silica, Chrysanthemum Parthenium (Feverfew) Flower/leaf/stem Juice, Glyceryl Behenate, Phenethyl Alcohol, Caprylyl Glycol, Cetyl Dimethicone/bis-vinyldimethicone Crosspolymer, Acrylates/dimethicone Copolymer, Sodium Chloride, Phenoxyethanol, Chlorphenesin.

J.R.S. Gordon, J.C. Brieva, Unilateral Dermatoheliosis, The New England Journal of Medicine (2012), DOI: 10.1056/NEJMicm1104059

Adapalene 0.3% may help improve the appearance of atrophic acne scars

A group of researchers sponsored by Galderma, a subsidiary of Nestle, have published the results of a series of experiments looking at the effect that Adapalene had on the prevention and treatment of atrophic scarring as well as acne.

Source: Art of Dermatology

Atrophic scarring is caused by a loss of tissue, so they can appear as sunken areas in the skin or even as holes, commonly referred to as ‘ice pick’ scars.

There were three experiments in total, a pilot study with 20 participants that compared Adapalene 0.3% gel compared to a control vehicle, another pilot study with 31 participants comparing Adapalene 0.1% and Benzoyl Peroxide 2.5% gel with a control vehicle, and a larger study with 54 participants comparing Adapalene 0.3% and Benzoyl Peroxide 2.5% gel with a control vehicle.

All three experiments were pre-registered on which helps reduce reporting bias. Often there is no incentive or reason to report on data from an experiment if there is no effect.

I’m going to focus on the latter paper as it has the most statistical power (> 80%) and the most clinically relevant results.

In brief, the experiment using Adapalene 0.1% with Benzoyl Peroxide 2.5% gel showed no change in the amount of atrophic scarring after 6 months of treatment, but people using the vehicle control saw an increase in scars (about 2 more scars after 6 months).

In the pilot study with Adapalene 0.3%, participants and investigators saw an improvement in scarring assessments at Week 1 and Week 24.

All three studies found a clinically relevant and statistically significant reduction in acne lesions for those using any Adapalene based gels.

With the Adapalene 0.3% with Benzoyl Peroxide 2.5% gel study, there was a statistically significant improvement in the scar assessment as early as Week 1.

By the end of the experiment at Week 25, there was a 15.5% decrease in a validated scar assessment scale – this worked out to about a mean decrease of 2 acne scars per half of the face.

Participants applied the Adapalene gel to only half of the face and the vehicle control on the other half, the researchers believe that if participants had applied the Adapalene gel to the whole face, there would be a decrease of a mean of about 4 acne scars for the entire face.

For the vehicle control side that contained no Adapalene, participants saw an increase of about 1.5 acne scars at the end of 24 weeks.

In terms of non-validated assessments, the amount of patients who responded to “How visible are the indents or holes to you?” with “A little visible” increased from 37.5% at Week 1 to 62.1% at Week 24.

Because some atrophic scarring can resolve on its own, the researchers believed the decrease in scarring with the Adapalene 0.3% and Benzoyl Peroxide 2.5% gel could be due to an increase in the speed of this resolution. For older scars, they believe that the Adapalene gel could be due to remodelling the dermis of the skin (possibly through stimulation of procollagen), improving their appearance.

Another factor would be the reduction in inflammatory acne lesions which could lead to new atrophic scarring formation.

The researchers point out that scar improvement was seen past 3 months, and that people using Adapalene may consider using the product for longer than 6 adapalene to help improve and prevent the appearance of atrophic scarring

In the US, Adapalene is now available over-the-counter as Differin with Adapalene at 0.1%. If you have moderate-to-severe acne with atrophic scarring you may consider speaking to your doctor and getting a prescription for the stronger 0.3%.

In terms of other retinoids, the researchers point out that there isn’t much research on topical use and improvement in atrophic scarring. For tretinoin I did find two studies, but they included other interventions in combination with the tretinoin. One used iontophoresis to enhance the penetration of tretinoin, and another used tretinoin in combination with microneedling. Both studies found improvement in atrophic scarring. Adapalene and other retinoids activate some of the same receptors, and since topical use of tretinoin has shown to increase procollagen as well, it’s likely that it will provide improvement on atrophic scarring as well.

B. Dreno, J. Tan, M. Rivier, P. Martel, R. Bissonnette, Adapalene 0.1%/benzoyl peroxide 2.5% gel reduces the risk
of atrophic scar formation in moderate inflammatory acne:
a split-face randomized controlled trial, Journal of the European Academy of Dermatology and Venereology (2016), DOI: 10.1111/jdv.14026

M.J. Loss, S. Leung, A. Chien, N. Kerrouche, A.H. Fischer, S. Kang, Adapalene 0.3% gel shows efficacy for the treatment of atrophic acne scars, Dermatology and Therapy (2018), DOI: 10.1007/s13555-018-0231-8

B. Dréno, R. Bissonnette, A. Gagné-Henley, B. Barankin, C. Lynde, N. Kerrouche, J. Tan, Prevention and reduction of atrophic acne scars with adapalene 0.3%/Benzoyl peroxide 2.5% gel in subjects with moderate or severe facial acne: Results of a 6-month randomized, vehicle-controlled trial using intra-individual comparison, American Journal of Clinical Dermatology (2018), DOI: 10.1007/s40257-018-0352-y

Comparison of skin hydration in combination and single use of common moisturizers (cream, toner, and spray water)

What’s the best way to organize your skincare routine? Should we layer from thickest to thinnest? Where does sunscreen go?

I’ve been asked this a lot and I don’t have the answer. Most research on skincare application is done with just one product. Sunscreens are always tested on clean skin with no other products. If you want to get as close to the protection on the label, it’s best to recreate the conditions it was tested on, which means applying it on clean skin and not following it with anything else. The same applies for most cosmetic products as well.

That’s not realistic for everyone and many of us enjoy using multiple products. But the reality with a lot of the advice found online and from experts is that it’s just advice and often isn’t based on evidence – especially scientific evidence.

A group of Chinese researchers performed an experiment looking at the effect of different combinations of three products (moisturizer, toner, and mineral water sprays) and different application routines on skin moisture. Keep in mind that the only endpoint measured was stratum corneum moisture measured by the Corneometer, a capacitance measuring tool often used in cosmetic research. This experiment doesn’t provide any insight beyond skin moisture, like skin penetration of an active affected by combination or routine, for example.

20 female volunteers participated in this experiment. Eight 3-by-3 cm squares were drawn on the legs and forearms of each volunteer and were randomized to receive eight different routines and combinations – including a square with no product applied, acting as a control. The baseline moisture levels of the squares were measured and categorized into ‘normal’ or ‘dry’ by a limit of 35 a.u. (a measurement unit used by the Corneometer).

The 8 different combinations and routines are as follows;

Toner and Toner reapplied every 2 hours (T-T)
Cream then Toner together (C+T)
Toner only (T)
Cream only (C)
Cream then Water reapplied every 2 hours (C-S)
Untreated (Control)
Cream and Toner reapplied every 2 hours (C-T)
Toner then Cream together (T+C)

Stratum corneum moisture levels were measured every 2 hours, including a baseline, and participants were kept in a 22 °C room with a 50% humidity.

The products included in the test were a Winona brand Cream with the ingredients:

Aqua, Glycerol, Butyrospermum Parkii Oil, Dimethicone, Glycereth-26, Tridecyl Trimellitate, Pentylene Glycol, Hexyldecanol, Sucrose Polystearate, Diethylhexyl Cyclohexane, Petroleum Jelly, Tocopheryl Acetate, Prinsepia Utilis Royle Oil, Portulaca Oleracea Extract, Beta Glucans, Sodium Hyaluronate, Cetylhydroxyproline Palmitamide, Alpha Bisabolol, Cetearyl Alcohol, Hydrogenated Polyisobutene, Acrylamide, Acrylamide/ammonium Acrylate Copolymer, Acrylates/c10-30 Alkyl Acrylate Crosspolymer, Tween 20, Xanthan Gum, Disodium Edta, Polybutene, Polyisobutene, Butyl Stearate, Stearic Acid, Phenoxyethanol, Ethylhexylglycerin

a Winona brand Toner with the ingredients:

Aqua, Pentylene Glycol, Glycerol, Glycereth-26, Trimethylpentanediol/adipic Acid/glycerin Crosspolymer,
Portulaca Oleracea Extract, Beta Glucan, Sodium Hyaluronate, Hydroxyethyl Cellulose

and Avene Thermal Spring Water was used as the Mineral Water Spray.

While applying any form of skincare product created an increase in skin moisture in dry and normal skin, some combinations were significantly more effective than others.

Table VI is mislabeled and is the data for Dry Skin

Because the normal or dry categories were determined by Corneometer, there’s no way to self-categorize unless you have a Corneometer handy.

From this experiment, the increase in moisture from Cream then Toner, or Toner then Cream, or Cream only were about the same. This implies that the total amount of cream and toner applied is more important than the order of application. As well, this also implies that the increase in moisture is mostly from the cream and not the toner.

The researchers speculate that the increase in moisture reaches a peak depending on factors like the environment which slowly declines after application. Toner on its own did increase moisture of the skin, but even when combined with cream never surpassed the moisture gained from cream alone.

In terms of supplementation of with Water or Toner, the greatest increase in moisture was achieved with application of a Cream then Toner every 2 hours. Supplementation of Water after Cream application reduced skin moisture with each application. Toner with additional Toner supplementation increased skin moisture over time, but was still less than Cream and Toner.

I think reading descriptions of the effects is likely a bit confusing, so I encourage you to use the interactive charts to compare different applications.

Also keep in mind that this experiment used three specific products and concentration of ingredients will vary between products. So it’s best to use this information as a guideline, but not a rule.

Li Yuanxi, Wei Hua, Lidan Xiong, Li Li, Comparison of Skin Hydration in Combination and Single Use of Common Moisturizers (Cream, Toner, and Spray Water), Journal of Cosmetic Science (2016), PMID: 29394018

US FDA warns that biotin supplements can interfere with lab tests

Are you taking biotin for your skin and nails? Be aware that biotin supplements can interfere with many lab tests. Some of the currently known interactions are tests measuring amounts of troponin, which are often used to diagnose heart attacks. Biotin supplements may also interfere with tests measuring hormone levels involving the thyroid.

The FDA is warning and helping to raise awareness of this side-effect,

“Biotin in blood or other samples taken from patients who are ingesting high levels of biotin in dietary supplements can cause clinically significant incorrect lab test results. The FDA has seen an increase in the number of reported adverse events, including one death, related to biotin interference with lab tests.”

Their recommendation for consumers is to talk to their healthcare provider about biotin supplements and for healthcare professionals to report adverse events to the FDA through the MedWatch report system.

I know supplements seem like an effective way to boost your beauty, because who doesn’t like the concept of beauty from within? But be aware that supplement claims are not regulated by the US FDA, nor do they require testing or approval.

“Federal law does not require dietary supplements to be proven safe to FDA’s satisfaction before they are marketed”

“For most claims made in the labeling of dietary supplements, the law does not require the manufacturer or seller to prove to FDA’s satisfaction that the claim is accurate or truthful before it appears on the product”

The US supplement industry is huge, poorly regulated, generally poorly backed by research, and has large profit margins. It’s easy to see why it can be an attractive market to enter, but don’t trust your health to anecdotal evidence.