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.
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
If you follow my Instagram you’ll know that I’ve been on a bit of a sunscreen bender. I’ve been trying to find a replacement for the Ombrelle Complete Kids SPF 50+. While I like that it has the modern UVA sunscreen filter Mexoryl SX, its cheap price and local availability…the texture leaves me wanting. It is thick, has a slight white-cast, becomes very shiny throughout the day because of its high glycerin content.
I was recently sampled a bottle of the Anthelios Ultra-Fluid Lotion SPF 60 and loved the invisible finish as well as its Mexoryl SX and XL content. I ended up gifting it though, because its high price meant it would not be a product I’d likely to repurchase. I found myself rationing it and probably not using enough to get the protection on the label.
I wanted to see if there were other sunscreens in La Roche Posay’s Anthelios line that had a similar finish but was more affordable. Oddly though, the Canadian La Roche Posay website doesn’t list the ingredients for their sunscreens! So, I headed to my local Shopper’s Drug Mart and took some photos. I’ve transcribed the ingredients here for your reference as well 🙂
The Anthelios XL Melt-In Cream SPF 45 in 100 mL size is not on the Canadian La Roche Posay website, but was available in the Shopper Drug Mart when I visited. The photo I have here is old, the packaging has been updated to match the Anthelios XL Melt-In Cream SPF 60. I’m not sure if this means it is being discontinued or not.
I’ll be posting a review of the products that I tried shortly, as I’m still in the process of testing one (The Anthelios Mineral Tinted Anti-Aging Primer SPF 50 for the curious!)
Mexoryl SX and XL are two patented sunscreens that are only used in the L’Oreal family of brands which includes La Roche Posay and Garnier Ombrelle. They are similar to Tinosorb S and M, but not the same. They tend to offer better UVA protection, as well as greater photostability, and less skin penetration.
Anthelios Ultra-Fluid Lotion SPF 50 For Body, 125 mL
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
Octocrylene
Avobenzone
Octinoxate
Octisalate
Oxybenzone
Homosalate
Mexoryl SX
Mexoryl XL
Tinosorb S
Tinosorb M
…
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
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.
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 very similarly – 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 or 320 nm and UVA is between 315 or 320 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.
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.
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.
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.
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.
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%) 6, 7. 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.
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.
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!
Cynthia had some questions about spray sunscreens after she got sunburned using one. She wanted to know if they work differently than other types of sunscreen, if they were worth using, and how to use them properly…so I helped her find answers!
