What lies beneath the “SCIENCE!”

OK, this post is going to be a bit more personal – because frankly this is something that’s been on my mind for quite some time and I think really needs to be discussed.

There’s a big problem in science-based beauty writing – especially from retailers, and I think it boils down to one big issue: Bias.

Science writing has always been difficult. It’s the translation of an experiment or analysis that’s very specific, distilled down to its essential point, and then presented in a way that will attract clicks.

“Moon leaf extract treats acne” is a much more appealing story than “Moon leaf extract reduces ratings on an acne severity grading scale compared to a placebo…in this study on Japanese people…but there was no effect on the Caucasian people in the study…it might also be due to changes in the weather – we don’t know. This is a preliminary study and another group should replicate it to validate our results. P.S. Our moon leaf extract may have been contaminated.”

You tend to lose all the nuances of a study once you summarise it into a single sentence. Often those nuances are important. This is something I worry about when writing for other websites and when I’m quoted in articles. Editors want clean and strong facts, and readers or customers want definitive and clear advice. Now add on to this the issue of bias, when most of us sit down to write we have a goal or idea and, we consciously or not, tend to focus on research that supports it. Writing a piece on green tea? I may read the supportive studies more closely or dismiss and be overly nitpicky with the studies that showed negative or no effect. Promoting a product that contains green tea? That bias presumably becomes stronger.

We’re humans, it’s hard to be impartial. I’m biased, I certainly have conscious ones and I definitely have unconscious ones. Do I like niacinamide based on its research? Or have I spent more time reading about niacinamide because I’ve been told it was well-researched? Do I favour my own formulations over others and do I lose out on improving my own formulations because of this bias?

Cosmetic research as a whole is neither vigorous nor impartial. It’s often funded by the manufacturer or a brand that is promoting its use. Most research on cosmetic ingredients extends to a single study – that will never be replicated. Most cosmetic research isn’t even done on humans – it’s performed on cells, on models, on animals, on plates of plastic. Most cosmetic products are studied in isolation.

It’s really difficult to take this loose, ephemeral, wishy-washy data and give a hard answer – that is unless you’re comfortable leaving out the gaps in the data, confounds, and specific conditions in the study, and unfortunately some science-based writers and retailers are. I get it – it’s not a great feeling to have someone reach out to you for advice and give them an answer that is at its core a long winded sigh of ‘Mayyybbbbeeeeeee’. That I can sympathise with, I can’t sympathise with people or companies who misconstrue or occlude information to position themselves as an expert or to sell a product.

I’m considering taking “skincare expert” out of my headline because I don’t think I am one – I’ve been told an “expert” just needs to know 1% more than the population, but I don’t think that’s enough. I think “expert” implies someone that has answers – and answers I do not have. What I do have is results from other people’s research, an opinion, and a desire to share both.

I want to be very clear: I know there are many writers out there that do seek out research, are curious, do their best to read it, understand it, and explain it to their readers. I also understand that not everyone has journal access or a relevant background. To them, I say get in touch with me – and I will help you get access to the paper and explain concepts. My issue is with the writers and companies who do have access, who twist and misconstrue, who leave out information that doesn’t support their view, those who are satisfied without questioning their conclusions, who write too confidently, who are OK with presenting a question as a fact, and who should know better.

So to my fellow writers, these are my suggestions to help our readers and customers make better beauty and skincare decisions

Clear and functional sources

Be proud of your sources, don’t source-puke a long list of unclickable, poorly formatted text in the hopes that people will be daunted and just trust what you wrote. Don’t just link to the journal’s homepage or a textbook. Take the effort and help people find where you found your information.

We live in the age of Digital Object Identifiers (DOIs), it’s a permanent link that will always point to that resource – even if it gets moved to a new location. Use them! Or at least stick to a style guide for your sources, the ACS style guide is commonly used.


Source and quote material that is relevant to your topic. Don’t source tangential things to try to make your writing look more researched. Was the experiment performed on humans? If not, you should point that out. Was it performed on humans, or animals, or cells? Was it a review of other research?

Often results from experiments on cells or animals are presented in a way to make us expect the same results when applied to our skin. Unfortunately, these results don’t always predict the results we can expect on humans. These types of studies can be useful in discovering how or why an ingredient works the way it does or if it’s possible for an ingredient to work – but they can’t replace results observed on actual people.

A review of ethanol’s effects on liver cells has been presented as evidence that ethanol applied onto the skin will cause the same damage – while there is a possible mechanism, that study isn’t strong evidence. Our skin acts as a barrier, ethanol evaporates quickly, other skin components like hyaluronic acid may reduce the effect, and human skin cells may respond differently than liver cells – these are just some factors that can change ethanol’s effect when put on our skin – but aren’t often mentioned.

Scrutinize yourself

We all make mistakes and we don’t all have editors or peers who can double-check our work. Saying something that isn’t common knowledge or you’re unsure of? Take a quick hop into Google and confirm it, otherwise, you might mischaracterize copper gluconate as a copper peptide.

If you’re citing research, read it! Finding a line that supports your point and skipping the rest of the paper is irresponsible, can be misleading to your readers, and most of all you’ve done yourself a disservice by missing out on some valuable knowledge.

Search broadly

Research is not an easter egg hunt. Searching for “Vitamin C+ Hyperpigmentation” won’t give you an unbiased and complete result. Because of the way paper abstracts and titles are written, searching for “Vitamin C + Hyperpigmentation” will likely only return results where Vitamin C was found to have a positive effect on hyperpigmentation. 

Instead try a broader search like “Vitamin C + Cosmetic”, “Vitamin C + Topical”, or “Vitamin C + Skin”.

Stop “SCIENCING!” the shit out of things

It is absolutely OK to not know something, or to not have an answer, or to have an opinion that isn’t researched. You can be honest with your readers and customers, I think they’ll appreciate that. Your opinions as a person or brand are valuable – as long as they’re transparent. Don’t use science as a veil, science is a process of discovery and learning – not a marketing angle or sales tactic.

“It’s important to keep in mind as you study chemistry or any other science that scientific theories are not laws of nature and can never be absolutely proven. There’s always the chance that a new experiment might give results that can’t be explained by present theory. All a theory can do is to represent the best explanation that we can come up with at the present time. If new experiments uncover results that present theories can’t explain, the theories will have to be modified or perhaps even replaced.”

— John E. McMurry, Chemistry (7th Edition)

Be honest

I think this is something that I can improve on as well. I will try to make it clear when I’m unsure about something and when I come across research that doesn’t “prove my point”.

Along those lines, I’d also like to thank you, the reader,  for your wonderful questions. There are often times when I get a new insight from a question, or it makes me realise that there’s a gap in my understanding.  I would love to give you answers to all of your questions, but I don’t have them. Sometimes I can only show you a map, but I can’t mark out the path. My broad advice is to let go of the notion of a “perfect routine” or “perfect product”. While the search for the perfect routine or skin care product isn’t a mythical quest – we’re not there yet. We don’t even know for sure if it’s better to apply a moisturiser before or after sunscreen – we have some educated guesses, but no strong proof! We’re even further from an answer that would apply to all sunscreen and all moisturiser combinations.

Skincare, as it is now, is a field of ‘maybes’. Maybe some of those expensive and rare botanical extracts have amazing anti-ageing effects and maybe it’s just the glycerin in your lotion that’s making your skin glow. Many skincare questions don’t have real answers yet and there’s even less information on whether or not an ingredient is better than another.

You should think about what your ‘evidence filter’ is set to. Is skincare fun and exciting for you? Do you have the budget and time to try newer and more novel ingredients? Then set your filter wider, enjoy the cornucopia of beautiful and fun products out there. Enjoy the process of applying them to your skin, of searching for them, of reading about other people’s experiences with them.

If that’s not what you want, then set your filter tighter, use ingredients that have more research on them – like a sunscreen with strong UVA and UVB protection and prescription retinoids. Take fewer risks and spend your money on skincare that has been shown to work for most people. You may be missing out on some truly effective ingredients, but you’re also avoiding ingredients that are just marketing.

In the long-run who will benefit more from their skincare routine? The person that seeks out the many novel and exciting products, or the one that picks the few researched and qualified products?

We just don’t know.


“Physical” vs. “chemical” sunscreens and other sunscreen myths

Titanium dioxide and zinc oxide are often categorised as “physical” sunscreens, whereas every other sunscreen used is considered a “chemical” sunscreen.


“Physical” Sunscreens “Chemical” Sunscreens
Zinc Oxide
Titanium Dioxide
Mexoryl SX
Mexoryl XL
Tinosorb S
Tinosorb M

You’ll often find different rules and advice for using “physical” and “chemical” sunscreens. One dermatologist says that you need to apply less physical sunscreen compared to a chemical sunscreen. There’s also the belief that “physical” sunscreens provide protection instantly, don’t absorb into the skin, don’t degrade in the sun, and don’t need reapplication.

These are myths and are not backed by research or chemical knowledge. By following these rules (or myths) you’re not using your sunscreen to its greatest effect!

“Physical” vs. “Chemical”

Dividing sunscreens into “physical” and “chemical” isn’t the best way to do it. These two categories overlap completely. If we were to draw a Venn diagram of the two groups, it’d look like this

Sketch (1)

Chemicals are physical – they have a mass and take up space. On the other end, the “physical” sunscreens titanium dioxide and zinc oxide are chemicals, you can find the elements titanium and zinc on the periodic table.



It’s sometimes explained that titanium dioxide and zinc oxide are suspensions of particles, they don’t dissolve or form solutions like chemical sunscreens. This is true and their even distribution in the sunscreen formula and on the skin is very important – poor distribution can greatly reduce how much UV protection titanium dioxide or zinc oxide can provide on the skin.

However, there are caveats, sunscreens like Tinosorb M (INCI: Methylene Bis-Benzotriazolyl Tetramethylbutylphenol) also exist as particle suspensions – not solutions. Tinosorb M comes as a very fine suspension of particles in water. So, if you were to draw the line based on that you’d have to include Tinosorb M,  a “chemical” sunscreen with the “physical” sunscreens.

What does differentiate titanium dioxide and zinc oxide then? Well, they’re both metal oxides or metals combined with oxygen. Metal oxide sunscreen doesn’t have the same ring to it, but there is another way to describe them.

Inorganic vs. Organic

In marketing, organic is a label that describes how something is produced – often with a safe-list of chemical treatments and approved practices.

In chemistry, organic means the chemistry of compounds that contain carbon. Titanium dioxide and zinc oxide don’t contain carbon. They’re made up of metal and oxygen and classified as inorganic.

Marking the categories as organic and inorganic makes more sense because all of the sunscreen chemicals used contain carbon, except for titanium dioxide and zinc oxide.


Sunscreen Chemical Formula Composition
Zinc Oxide ZnO 1 Zinc + 1 Oxygen
Titanium Dioxide TiO2 1 Titanium + 2 Oxygens
Octocrylene C24H27NO2 24 Carbons + 27 Hydrogens + 1 Nitrogen + 2 Oxygens
Avobenzone C20H22O3 20 Carbons + 22 Hydrogens + 3 Oxygens
Octinoxate C18H26O3 18 Carbons + 26 Hydrogens + 3 Oxygens

Organic and inorganic is also a useful way to categorise sunscreens because the way that the carbon atoms are linked up in organic sunscreens is why they absorb UV energy. If you look at the chemical structure of an organic sunscreen like avobenzone you’ll see that they have single bonds alternated with double bonds.


This alternation or conjugation of the single and double bonds allows the molecule to absorb energy along the electromagnetic spectrum. The amount of conjugation determines which part of the electromagnetic spectrum they absorb, whether that be in the visible spectrum to produce a colour, or in the ultraviolet spectrum to protect our skin from UV.


Inorganic and organic neatly divide the two sunscreen types and are also descriptive. I know most companies won’t want to confuse their customers by labelling their 80% organic-certified sunscreen product with titanium dioxide as inorganic, but at least as sunscreen shoppers we can understand the difference!


Myths about using Inorganic vs Organic Sunscreens


“Inorganic sunscreen and organic sunscreens work differently”

Mostly Myth! It’s often said that inorganic sunscreens (titanium dioxide and zinc oxide) reflect UV off of the skin and organic sunscreens absorb UV and convert it into heat. In reality, for most of the UV spectrum they work very similarly.

Organic sunscreens absorb UV because of the way the bonds between their carbon molecules are arranged. The number of bonds between the carbon atoms in the sunscreen molecules and their conjugated arrangement give sunscreens their absorptive properties in the UV region of the electromagnetic spectrum. Remember that conjugated means alternating single and double bonds!

The energy from UV light promotes electrons in the conjugated carbon bonds of organic sunscreen molecules from a lower energy state to a higher energy excited state. The excited electrons in the bonds then relax or release the absorbed energy by stretching, vibrating, or bending – this turns that energy into heat.

In some cases, the organic sunscreen chemical can’t relax and release the absorbed energy by bending, stretching, or vibrating and the absorbed energy causes a change in its structure. This is what happens with avobenzone, it absorbs the UV energy and instead of relaxing, it changes its structure – and this new structure formed from avobenzone doesn’t absorb UV energy as well. As more and more avobenzone molecules’ structures change, the less UV energy is absorbed by the sunscreen formula. Some of the new structures formed from avobenzone are also more irritating and sensitising to the skin. Photo-stabilizers prevent this from happening by absorbing the energy from excited avobenzone and releasing it before its structure can change.

Inorganic sunscreens work the same way – even though their structure is different from organic sunscreens. Metal oxides, like titanium dioxide and zinc oxide, have solid structures made of alternating sheets of metal and oxygen atoms. The principle behind the UV protection is exactly the same as organic sunscreens. Instead of the arrangement and amount of carbon bonds, the particle size of the titanium dioxide or zinc oxide determines which parts of the electromagnetic spectrum it absorbs.

There is a strong belief that these inorganic metal oxide sunscreens act by reflecting UV light instead of absorbing it, but this isn’t the complete story. UV light is divided into UVB and UVA. UVB is between 280 to 315 nm and UVA is between 315 to 400 nm. Inorganic sunscreens predominately absorb in the UVB spectrum and reflect in the long UVA (above 360 nm) and visible spectrum. Only about 5% of UVB light is reflected by inorganic sunscreens and the remainder gets absorbed and converted – just like organic sunscreens.

The results of a measurement show how much energy is reflected by different types and sizes of titanium dioxide. The horizontal scale represents the electromagnetic spectrum with my yellow highlight marking the UV spectrum. The vertical scale represents how much of the energy is being reflected, the higher up on the chart – the greater the amount of reflection.

titanium dioxide2

Between 250 nm and 350 nm titanium dioxide reflects less than 10% of the energy. Between 350 nm and 400 nm there is more reflection depending on the form of titanium dioxide and the particle size. The anatase form of titanium dioxide exhibits more reflection than the rutile form of titanium dioxide. These forms have to do with the way the titanium and oxygen atoms are arranged in the titanium dioxide. Sunscreens often use rutile titanium dioxide because they are safer and less reactive.

The same is seen with zinc oxide, with most of the reflection being above 350 nm. The rest of the UV spectrum is absorbed.

zinc oxide

The high reflection above the UV spectrum (above 400 nm) into the visible light region of the electromagnetic spectrum is what causes the whitening effect and flashback when using inorganic sunscreens.

“You can use less of an inorganic sunscreen compared to an organic sunscreen”

Myth! All sunscreens are tested at the same density, which is 2 milligrams of sunscreen per square centimetre. That applies to inorganic, organic, spray, stick, lotion, wipes, etc.

If you want to get as close as possible to the protection on the label of the sunscreen product, you need to apply it at the same density it was tested at.


“Inorganic sunscreens sit on the skin. Organic sunscreens absorb into the skin”

Myth! Think of it this way, if we want to protect ourselves from the rain we need to hold the umbrella above our heads. Sunscreens work the same way, you want them to absorb the energy before they can reach our skin cells, particularly the living cells. The most effective way for this to be done is to have them on the surface of the skin in a continuous and even layer.

Both organic and inorganic sunscreen particles can penetrate into the upper layers of the skin. If and how much they penetrate is dependent on properties like their particle or molecular size as well as the overall sunscreen formula. This isn’t a desired effect and formulators work to reduce the amount that penetrates. Modern organic sunscreens often have larger molecular sizes, chemical and physical properties, or even coatings which make it more difficult for them to penetrate past the surface of the skin.

Keep in mind that skin penetration doesn’t mean that it’s causing harm to our bodies. There has to be a biological mechanism for it cause an effect. There is a lot current and ongoing research into this area, but we don’t have any strong answers yet.


“Inorganic sunscreens provide protection right away. Organic sunscreens need to activate on the skin”

Myth! Organic sunscreens and inorganic sunscreens absorb UV due to their electronic properties. There’s no activation or chemical reaction that occurs on the skin with organic sunscreens to create photoprotection.

We know this is true because we can measure how much UV is absorbed by an organic sunscreen off of the skin, like on a piece of clear plastic. Organic sunscreens will also prevent UV colour changing bracelets, beads, or stickers from changing colour.

Both inorganic and organic sunscreens will provide UV protection as soon as they’re placed on the skin. The reason why a wait time is part of the application instructions is to allow the sunscreen formula time to dry and form a film on the skin. This makes it harder for it to be wiped off and it also means it can dry to as even of a film on the skin as possible.

The more evenly distributed the sunscreen is on the skin, the more even the coverage and the greater the average protection. If we take 10 umbrellas and hold them over one person, that one person may remain very dry during a downpour but everyone else will get soaked – if we distribute the umbrellas evenly more people will remain dry. Photoprotection works the same way, it’s measured as an average – you don’t want some areas of the skin with more sunscreen and greater coverage at the expense of other areas with less sunscreen and less coverage.


“Inorganic sunscreens don’t need to be reapplied”

Myth! All sunscreens should be reapplied if you want to maintain photoprotection throughout the day. While it’s true that titanium dioxide and zinc oxide don’t change structure under normal UV radiation, that’s true for many organic sunscreens and sunscreen formulas as well.

The reason why reapplication is recommended is because we often don’t apply enough in the first place and it’s constantly being removed from our skin. Reapplication helps ensure that we have a minimum density of 2 milligrammes per square centimetre of sunscreen on our skin and that we maintain that density throughout the day.

We may not be conscious of removing our sunscreen, but touching our skin, putting on and taking off clothing, using our phones, sweating, eating…all these things will remove some of the sunscreen from our skin. Think about how the coverage of a foundation or lipstick changes throughout the day.

There is no clear answer as to when you should reapply your sunscreen. We all do different things throughout the day in regards to our skin, so the amount of sunscreen removed from the skin will differ from person-to-person and day-to-day. That’s why it’s difficult to have a single rule that will apply to everyone. Conclusions from studies vary in their recommendations for when and how often to reapply.

What you choose to do is up to you, but you should take into account how much UV you’re exposed to, how much you expect to be exposed to, and your activities. You should think about reapplying your sunscreen before going for a jog outdoors. Work in an office? Maybe reapply before you leave the office. What’s clear though is that you should definitely reapply after sweating, swimming, bathing, and abrasion (like laying on sand) – even if you are using a water-resistant sunscreen.

In the UK many sunscreens are marketed as ‘once-a-day’, but health organisations recommend disregarding that and still reapplying throughout the day.

I hope this post has helped you understand why calling some sunscreens “physical” and others “chemical” isn’t as descriptive as it could be, as well as why inorganic and organic sunscreens should be used the same way. Sunscreen is an important part of a skincare routine, and there’s a lot of conflicting advice on how to best use it. Understanding some principles will help you make sense of what is good advice and poor advice when it comes to sunscreen.

I’d also like to thank my friend Jonathon Moir for his help in editing this article.

Vintage skincare and beauty!

The Smithsonian museum has made their archive of historical beauty products public! The collection contains photos and information on balms & salves, as well as make-up, fragrances, and more.

Perusing the collection is a wonderful way to spend a Sunday afternoon, and it’s really interesting to see how products and design have changed – or haven’t.

Smith’s Rosebud Salve still looks the same, for example.


Smith’s Rosebud Salve

For “Chapped lips, face and hands, minor burns and scalds, bites and stings of non-poisonous insects”



Mentholatum, now owned by Japan’s Rohto (the makers of those minty-fresh eyedrops) is famous for their lip balms, decongestant rub, and ointments for sore muscles.


Mentholatum Tin

“Try Mentholatum for Head Colds, After-Shaving, Chapped Skin, Cracked Lips, Sunburn, Burns”



Yardley is one of the first companies to specialize in beauty products, established in 1770.


Yardley Complexion Milk

“A liquid skin cream, smooth & refreshing. Brings elasticity & lustre to a dried skin and forms a perfect face powder base.”



Petrolatum was “discovered” by Robert Chesebrough, after he noticed oil field workers rubbing the jelly on their hands to help heal wounds.


Vaseline Tube



Maybelline was commercialized by a 19 year old boy after he noticed his sister, Mabel, mixing vaseline with coal tar and using the mixture to coat her lashes.



Maybelline Cake Mascara



Gel cream blushes are making their way back into popularity, but this one was made back in the ’70s by Love Cosmetics, which was owned by a company which later became GlaxoSmithKline.


Love’s Cheek Gel in Pink Bronze



This liquid hose was meant to even out the skin tone of the legs, much like Sally Hansen’s modern aerosol version.


Vida-Ray Liquid Hose, Toasted Beige


I found an advertisement for this product in the 1945 Milwaukee Journal. During World War II, cosmetics became a luxury and some women used gravy browning to replace the now rare liquid hose.





There’s so too many other interesting finds to go through them all, but I’ve put some of my other top picks in this gallery.


One Hundred Assorted Beauty Spots by Johnson and Johnson
Zuane La Parot Rouge, Medium by Zuane Parfumers
Chen Yu Cloud Silk Make Up, Light Lotus #1 by Richard Hudnut
Jergens Face Powder, Pink Frosting by Andrew Jergens Company
Pond’s Make-up Pat, Peach by Pond’s Extract Company
Pearlized Chili Pepper Nail Hardener Enamel
Emile Mascara Remover
Airspun Face Powder, Suntan Golden Tone by Coty
Touch & Glow Liquid Makeup, Sun Bronze by Revlon
Pure Magic Super Cover Stick, Natural Fair by Max Factor and Company
Mary Kay Lip and Eye Palette by Mary Kay Inc., made in 1964
Sunscreen sticks arranged in a ring

What’s the best way to use stick or balm sunscreens?

Why choose a sunscreen stick or balm?

Sunscreens in a waxy and solid base are portable, easy to apply, and can offer good water-resistance. They’re a great way to protect the lips and the skin around the eyes, and are small enough to fit in your pocket.

They can keep sunscreen from running into your eyes!

Applied around your eyes stick or balm sunscreens can help prevent other sunscreens from migrating into your eyes and causing stinging or blurring.

Sticks or balms with higher melting points tend to be better at this task. Look for ones that are harder and don’t melt when you hold your finger to it.

No more stinging, squinting eyes!

Do I Need To Protect My Lips?

Yes! Just like the rest of your skin, your lips are susceptible to UV exposure. The lower lip especially is among the most exposed areas to UV on the face 1.

Lips lack some of the natural photoprotection that the rest of the skin has. There’s less melanin, which acts as a natural sunscreen by converting UV energy into heat 2. Also sebaceous glands are absent. The sebum produced by these glands contain photoprotective antioxidants like Vitamin E 3,4. The skin of your lips is also about a third thinner than the rest of your skin.

Like the rest of your skin, UV exposure increases your risk of developing skin cancer. Lip cancers represent 0.6% of skin cancer cases, and are most common in men over 50 5. Thankfully, they have a very high cure rate (90-100%) 67. Oral melanoma is much more rare and vastly more lethal, and is also linked to UV exposure 8. If you do find new spots on your lips or inside your mouth – please get it checked!


Interestingly, one study found that minimum amount of UV energy to cause marked redness was 25% lower on the lips compared to back skin 9. The amount of skin reddening is used to determine SPF. What this could imply is that our lips have better protection against UV, from something other than skin thickness, antioxidants, and melanin content. However, only the upper lip was tested, the comparison of protected and unprotected skin was performed on the upper and lower lip, and the analysis was performed by different labs.

How much of the stick or balm do I need to apply?

SPF and UVA protection are tested at a global standard of 2 mg/cm².

This information isn’t too useful for the lips, their size varies greatly, and you can’t really measure the amount of product easily.

One would assume that sunscreen sticks are designed to supply the required 2 mg/cm², but unfortunately that is not the case.

A group of researchers studied the amount of sunscreen applied when using a stick or balm. They found that the median amount applied was only half of the required density 11. 3 of the 28 participants applied close to the required amount, with 1 participant applying a whopping 2.5 mg/cm².

Based on this, if you want the amount of photoprotection labelled you’ll have to apply the sunscreen twice.

This applies to all types of sunscreen sticks or balms. How stiff or soft the sunscreen was didn’t affect how much was applied. Despite this, researchers recommended choosing a stiffer stick or balm. They suggest that softer and oilier products feel like they deposit more sunscreen, which isn’t true!

How often should I be re-applying?

Unfortunately there isn’t a convenient recommendation that’s based on a lot of strong scientific evidence, however at a minimum you should tryt to reapply the sunscreen after 15 minutes to 2 hours of cumulative UV exposure 12.

Since sunscreen sticks or balms are easily wiped off, you should reapply after eating, drinking, wiping your mouth and anything else that may remove the product (like kissing!).

How to choose a sunscreen stick or balm

Look for a product with an SPF of 30 or greater. You want a product with full coverage of the UV spectrum, UVA and UVB. Most sunscreen stick or balms available in the US and Canada only provide strong UVB protection, this is especially true of products that are SPF 15.

In the US and Canada, look for products that have the “broad spectrum” labelling. While it’s only a relative assessment of the UVA protection, it’s the only information we have regarding the UVA protection. Canadians have access to products containing better UVA sunscreens like Tinosorb S and M, as well as Mexoryl SX and XL. La Roche Posay, Avene, and Vichy have these sunscreen chemicals in some of their formulations.

Other countries have different standards for UVA protection labelling. In the UK and Europe look for a high UVAPF, PPD, or the UVA circle logo. In Japan look for products with a PA rating of +++ or higher.

In terms of texture of the product, it doesn’t make a significant difference in how much is applied per swipe. However, products with a higher melting point (they’ll feel stiffer and don’t melt as easily when you touch them), may last longer on the skin as they’re less easily wiped off.

I personally switch between Bioderma’s Photerpès SPF 50+ with UVAPF 38, Avene’s Haute Protection SPF 30, and La Roche Posay’s Anthelios Targeted Protection Stick SPF 60.

Can you provide an overview of the study?

Assessment of thickness of photoprotective lipsticks and frequency of reapplication: results from a laboratory test and a field experiment

The two products used in the study were: Labello’s UV-Alpin SPF 30 Sun-Block and Garnier’s Delial Sun Stick SPF 16 (both discontinued).

The Labello product has a higher melting point than the Delial product, it feels firmer and less oily.

The study was performed in two parts:

The first experiment was performed in the laboratory. 25 students and 5 professors were asked to apply the sunscreen in front of a mirror, without instruction about how application relates to photoprotection. After the sunscreen was applied, the stick was weighed to see how much of the product was used. The mass of product used was divided by the surface area of their lips to calculate the density. The subjects’ lip area was calculated by having them kiss a piece of paper while wearing a colored lipstick. Each subject was asked to apply the sunscreen 10 times.

The second experiment was performed during a 6 day skiing trip with 18 students. For 3 days they applied one stick sunscreen, and for the remainder of the trip they applied the other stick sunscreen. The amount of times the sunscreen was applied was recorded. The difference in mass of the sunscreen sticks was divided by 3 (for each day it was applied) to get the average mass used per application. The average mass used per application was then divided by the surface area of their lips (again by having them kiss a piece of paper wearing lipstick).

In the lab, the median density of application was 0.98 mg/cm² for the Labello product and 0.86 mg/cm² for the Delial product. There wasn’t a statistically significant difference of density between the two products, so it seems the hardness of a product doesn’t make a large difference. Other factors like age, sex, skin type, or using lipstick didn’t affect the density of application either.

On the skiing trip, the median density of application was 1.58 mg/cm² for the Labello product and 1.76 mg/cm² for the Delial product. Participants applied the softer Delial product more frequently, but there still wasn’t a statistically significant difference of applied density between the two products. It’s important to note that the temperature was between -6C and 4C. The sunscreen sticks get harder when cold, which could make them transfer less product onto the lips per application. As well the colder, windy environment may have prompted participants to apply the product more frequently – not so much for photoprotection, but for protection from moisture loss.

How To Research: Just Reading The Abstract Isn’t Good Enough

Abstracts are a short summary covering the background, methods, results and conclusions of a scientific paper. While abstracts are easy to find, sometimes they are the only information from a paper that’s accessible. It’s important that our knowledge is accurate, as this informs our purchasing decisions and our understanding of skin care.

We assume that the information in abstracts is accurate…right? Well, not all the time.

A study examined six peer-review journals and found inaccuracies in 18% to 68% of the abstracts.

Two conditions were considered inaccuracies in this study:

The first kind of inaccuracy was when data was mentioned in the abstract that differed from the data contained in the full paper – rounding of numbers weren’t considered inaccurate if the full paper contained the correct number.

The second kind of inaccuracy was when data was mentioned in the abstract, but couldn’t be found in the full paper itself.

Keep in mind this study only looked at numerical inaccuracies. It’s entirely possible to have factual inaccuracies, where the abstract states or exaggerates a conclusion that the data from the full paper disagrees with.

Another study examining dermatology journals found varying levels of quality among abstracts.

It’s worthwhile to take the time to read the full paper, especially since researchers take the time to expand on their conclusion in the ‘Discussion’ section as well as point out the weaknesses or gaps in their paper. You can also glean important information such as whether or not the subjects in the study are representative of you. If the language or information is daunting, focus on annotated charts and graphs as these can provide a clearer idea of the results.

This also extends to references! If a researcher references another paper they often try to summarize the results, but sometimes in the simplification they can leave out vital information.

For example, while I was researching the skin benefits of consuming green tea and its extracts on human skin, I came across a cosmetic dermatology textbook which cited a 2 year long study that showed that green tea extracts were beneficial for reducing photodamage and wrinkles. Great! I thought.

Once I pulled up the actual reference the actual conclusion was that at the end of the 2 years there was no difference in the group that received the green tea extract, and those that did not. At the 6 month and 12 month point they did find an improvement in the group that received the extracts – for overall sun damage as well as erythema (skin redness) and telangiectasias (broken capillaries), but no differences in wrinkling.

I’m sure the textbook author had not intended to misconstrue the research, and it was perhaps editorial oversight – but it also highlights why if you find something that strikes your interest, you need to spend the extra time and read it in greater depth.

OK, But What If I Don’t Have Library Access?

There are online journals that provide open-access to the public:

The Cochrane Library – Skin
Journal of the American Academy of Dermatology
International Journal of Cosmetic Science
Archive of the Journal of Cosmetic Science
Clinics in Dermatology
Cosmetic Dermatology
Journal of Cosmetics, Dermatological Sciences and Applications
Journal of Cosmetic Dermatology
Dermatology and Therapy
Journal of Clinical and Experimental Dermatology Research
Clinical, Cosmetic and Investigational Dermatology
Nature: Communications

There are also databases that catalogue open-access papers:

Google Scholar
Directory of Open Access Journals
Highwire – Stanford University

Research can be incredibly confusing and non-conclusive, but that’s also what makes it so interesting and dynamic!

Sunscreenr: The gadget that shows you gaps in your sunscreen application

This is really cool! I came across this project on Kickstarter a few months ago and it looks like they now have a functioning prototype.



How does it work? From my understanding most smartphone cameras use a CMOS type sensor – which is sensitive to both UV and IR wavelengths. In order to create images that match what we can see, special filters are applied to filter out the UV and IR. Humans can’t perceive UV or IR, but other animals can — like the damselfish!

So the Sunscreenr seems to just be a smartphone camera without the UV filter! That means that anything we apply to our skin that absorbs light in the UV spectrum will show up as darker on the device.

The team at Sunscreenr recently took it to Mashable for a demo and there’s a video of it in action below:


The projected price is $109 USD, and the creators say if it is ever mass produced it could go down to $20 USD.

Personally, I think I would buy one at the $20 to $30 USD price-point. While it is useful, it won’t be able to catch an important aspect of sunscreen – which is the density or how thickly it’s applied.

It’d be great if someone could invent a camera that could measure how much UV is being absorbed – but I don’t think that exists yet.

I’m also waiting for the day where smart mirrors because more ubiquitous – imagine a mirror that can show you where you’ve applied your sunscreen and how much!

People are already DIY-ing their own smart mirrors, so hopefully the day that putting on sunscreen is an exercise in pure elegance is near!