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.

Visualizing how a daily sunscreen can protect the skin from UV damage

Optical coherence tomography and reflectance confocal microscopy can be used to non-invasively to visualize deep into the skin. Using these techniques we can actually see changes in the structure of the skin and its cells.

This group of researchers with funding from La Roche Posay used the imaging techniques to compare the effect of UVB exposure on skin protected with a high SPF and UVAPF sunscreen and skin that wasn’t protected.

What they found was that doses of UVB that caused long-lasting erythema (redness) caused morphological changes in the skin. Changes observed were spongiosis (abnormal accumulation of fluid), microvesicles, sunburn cells, and blood vessel dilation. None of these were observed in skin that was protected by the sunscreen.

A minimal erythemal dose or MED is the amount of UV energy that causes long-lasting redness in the skin. Just 1 MED was enough to cause morphological changes and 2 caused significantly more. This also relates to SPF. An SPF of 2 would provide enough protection to protect an average population against 2 MEDs.

If reducing your risk of developing skin cancers and preventing photoaging are a goal of yours – this is a great reminder and justification to wear your sunscreen daily!

Antonio Gomes-Neto, Paula Aguilera, Leonor Prieto, Sophie Seité, Dominique Moyal, Cristina Carrera, Josep Malvehy, Susana Puig, Efficacy of a Daily Protective Moisturizer with High UVB and UVA Photoprotection in Decreasing Ultraviolet Damage: Evaluation by Reflectance Confocal Microscopy, Acta Dermato-Venereologica (2018), DOI: 10.2340/00015555-2736

What’s causing sunscreen to stain clothing?

Yellow stains on your clothing? Your sunscreen might be a culprit!

A group of researchers tested 32 commercial sunscreens for their ability to stain white and black 100% cotton.

Of the tested sunscreens; Alba Botanica Hawaiian SPF 50 Spray, L’Oreal Invisible Protect SPF 50, Solbar Thirty, and Aveeno Protect and Hydrate SPF 50 were among the most staining sunscreens.

The least staining sunscreens were; Cerave Baby, Solbar Zinc 38, Cerave Face SPF50, and Babyganics Mineral Based SPF 50

Using statistical analysis to group the sunscreens by sunscreen ingredients they created four distinct groups. Based on these groupings they tested 8 sunscreen ingredients; Avobenzone, Homosalate, Octinoxate, Octisalate, Octocrylene, Oxybenzone, Titanium Dioxide, and Zinc Oxide.

For white fabric; Avobenzone was a strong yellow stainer and so was Oxybenzone to a lesser extent. Titanium Dioxide and Zinc Oxide both left faint white stains.

For dark blue fabric; Avobenzone and Oxybenzone both left faint white staining, but Titanium Dioxide and Zinc Oxide left strong white stains.

The sunscreen ingredients were applied directly to the fabric, whereas in real-life it’s likely transferred to skin by friction and smearing throughout the day

A sunscreen that stains is by no means a reflection of its ability to protect your skin from UV. If reducing extrinsic photoaging is a goal, it’s important to use a sunscreen frequently. Often people are discouraged from using sunscreens because of the texture, scent, and in some cases staining of their clothes.

If staining is an issue I’ve had good luck with soaking it with 99% isopropyl alcohol and then a soak in sodium percarbonate (Oxiclean) or hydrogen peroxide.

Cornell also has a great stain guide for a myriad of stains.

Ginnetti M, Buhnerkempe M, Wilson M, The staining of clothing by
sunscreens: a pilot study, Journal of the American Academy of Dermatology (2018), doi: 10.1016/j.jaad.2018.02.022

Mushrooms aren’t people! Or why human clinical studies are the gold standard

Marketing language of skincare often leaves out on “what” the tests were done. Leading the consumer to believe that the testing was done on someone like them.

For many products aimed at treating hyperpigmentation, the claims are often based on the inhibition of tyrosinase, an enzyme found in plants and animals that plays a role in the creation of melanin. So it makes sense why inhibiting the effect of tyrosinase would lead to a decrease in melanin production in the skin. What’s often left out, is that most of these tests are performed on tyrosinase derived from the Agaricus bisporus mushroom.

What’s important to understand is that though the enzyme group may be the same, the structure and environment isn’t. Mushroom tyrosinase and human tyrosinase (hTyr) have different catalytic activities and substrate affinities.

Mushroom tyrosinase is easily accessed, commercially available, and cheap. Human tyrosinase until recently was difficult to produce and isolate.

As early as 2013, a group of researchers led by Petra Cordes were able to express hTyr in human kidney cells and then isolate them. This allowed them to 3D map the enzyme and use them in further tests.

Building upon this, scientists from Beiersdorf screened 50,000 compounds to see which ones effectively inhibited hTyr. What they found was interesting, but not surprising.

Some compounds which are very effective in inhibiting mushroom tyrosinase (like hydroquinone, arbutin, and kojic acid) had a reduced or minimal effect on hTyr.

Of the 50,000 compounds tested, thiazolyl-resorcinols were the most promising. They then modified it to be compatible with topical formulations leading to isobutylamido thiazolyl resorcinol.

An interesting thing they found about hydroquinone and its precursors like arbutin was their activity may be due to a cytotoxic effect on melanocytes. Their experiment showed a long-term reduction in melanocyte activity even after the hydroquinone or arbutin was stopped.

The group at Beiersdorf then went on to test 0.2% isobutylamido thiazolyl resorcinol on a group of humans for 4 weeks and were able to see a statistically significant and clinically relevant decrease in hyperpigmentation.

It’s very likely that Beiersdorf will patent the use of isbutlamido thiazolyl resorcinol for treating hyperpigmentation, especially if further human clinical trials are positive, but their methods for performing this test on human tyrosinase in MelanoDerm skin models have been shared with the scientific community.

Mann T, Gerwat W, Batzer J, Eggers K, Scherner C, Wenck H, Stäb F, Hearing VJ, Röhm K-H, Kolbe L, Inhibition of Human Tyrosinase Requires Molecular Motifs Distinctively Different from Mushroom Tyrosinase, The Journal of Investigative Dermatology (2018), doi: 10.1016/j.jid.2018.01.019.

Does drinking more water make your skin more hydrated?

“Drink more water to hydrate your skin”. You’ve probably heard it, and it’s easy to see why this is common advice – it’s cheap, sounds right, and feels healthy…but is it true?

Researchers at the University of Berlin took a look at studies published in peer-reviewed journals that examined an increase in water intake and measurements of skin hydration. On Pubmed and Web of Science they found 216 records. Many of those were duplicates, unrelated, or didn’t have enough data. From those 23 were selected, many were dropped due to a high risk of bias…leaving them with 6.

With these 6 studies, of which 5 were experimental, the mean age of the samples ranged from 24 to 56. So if you’re much younger or older than that – these conclusions may not apply to you.

The experiments showed a slight, but statistically significant, increase in stratum corneum hydration when people drank an extra 1 to 2 litres of water a day. The increase was more significant if people were consuming low amounts of water previous to the experiment.

There was no difference in measurements of trans-epidermal water (TEWL) loss in any of the studies. TEWL is often used as an analogue of the skin’s barrier permeability and is a measurement of the amount of water evaporating from the skin. A decrease in TEWL is usually seen as a decrease in permeability.

Other studies looked at skin smoothness, skin roughness, and skin elasticity. While some of the studies showed slight positive effects when consuming mineral water, other similar studies showed no effect.

A couple papers looked at the effect of consuming water on the skin’s pH. In one experiment they found men had a slight decrease in skin pH when consuming 100 mL of water. And the other experiment found a decrease in skin pH when consuming 2.25 L of tap water, but not mineral water.

The researchers point out that measurement devices using electrical capacitance to measure stratum corneum hydration can be affected by dermal hydration. So the readings might be off. As well they point out that the “logical” thought of increased dermal hydration creating greater stratum corneum hydration isn’t necessarily correct. Hydration of the stratum corneum is more dependent on natural moisturizing factors, intercellular lipids, and the structure of the composing corneocytes.

Like most studies of this nature, their conclusion is “maybe” and “requires further research”. The researchers thought it’s possible that increased water intake could be increasing “deep” skin hydration, but unfortunately, the experiment reporting those results didn’t explain how that was measured – so it’s not strong evidence. As well, different types of water were used; each region’s tap water will be different, as will each source of mineral water.

I do want to touch quickly on hyponatremia – also known as “water poisoning”. When too much water (especially deionized) is consumed very quickly – electrolyte levels can drop drastically which can lead to fluid moving into cells causing damage to the body. While everyone is different, the amounts needed to cause hyponatremia are quite large – one paper reported on soldiers who had died from hyponatremia found that the amount consumed was 10-20 litres in a few hours and was combined with exertive exercise.

My thoughts? Adding a litre or two of extra water a day isn’t going to transform your skin – but it probably isn’t a harmful habit either if the intake is spread out throughout the day.

Akdeniz M, Tomova-Simitchieva T,
Dobos G, Blume-Peytavi U, Kottner J. Does dietary fluid intake
affect skin hydration in healthy humans? A systematic
literature review. Skin Res Technol. 2018;00:1–7.