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, http://www.cosmeticsandtoiletries.com/formulating/category/suncare/premium-the-quest-for-avobenzone-stabilizers-and-sunscreen-photostability-214405251.html

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

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

Canadian La Roche Posay Anthelios Sunscreen Ingredients

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

anthelios-body

Active Ingredients

Homosalate 10%, Oxybenzone 6%, Octisalate 5%, Octocrylene 5%, Avobenzone 3%, Ecamsule (Mexoryl SX) 2%

Other Ingredients

Aqua, Cyclopentasiloxane, Alcohol Denat., Cyclohexasiloxane, Styrene/Acrylates Copolymer, Silica, Dicaprylyl Ether, PEG-30 Dipolyhydroxystearate, Dimethicone, Triethanolamine, Glycerin, Nylon-12, Polymethylsilsesquioxane, Caprylyl Glycol, Dicaprylyl Carbonate, Disodium EDTA, Disteardimonium Hectorite, Dodecene, Isostearyl Alcohol, Lauryl PEG/PPG-18/18 Methicone, PEG-8 Laurate, Phenoxyethanol, Poloxamer 407, Poly C10-30 Alkyl Acrylate, Tocopherol. (Code F.I.L.: C182364/1)

 

Anthelios Mineral Tinted Anti-Aging Primer SPF 50, 40 mL

anthelios-mineral-tinted

Active Ingredients

Titanium Dioxide 25%

Non Medicinal Ingredients

Dimethicone, C12-15 Alkyl Benzoate, Dicaprylyl Ether, Dimethicone/Vinyl Dimethicone Crosspolymer, Talc, Triethylhexanoin, Isohexadecane, Styrene/Acrylates Copolymer, Hydrogenated Jojoba Oil, Aluminum Hydroxide, Stearic Acid, Aluminum Stearate, Alumina, Caprylic/Capric Triglyceride, Cassia Alata Leaf Extract, Diethylhexyl Syringylidenemalonate, Disodium Stearoyl Glutamate, CI 77491, CI 77492, CI 77499 / Iron Oxides, Laureth-4, Maltodextrin, PEG-8 Laurate, Polyhydroxystearic Acid, Silica Silylate, Tocopherol, Aqua. (Code F.I.L.: C179435/3)

 

Anthelios Dermo-Kids Lotion SPF 50, 150 mL

anthelios-dermo-kids

Active Ingredients

Titanium Dioxide 5.85%, Octisalate 5%, Drometrizole Trisiloxane (Mexoryl XL) 4.5%, Avobenzone 3%, Octocrylene 2.5%, Ecamsule (Mexoryl SX) 1.5%

Other

Aqua, C12-15 Alkyl Benzoate, Alcohol Denat., Caprylic/Capric Triglyceride, Isododecane, Propylene Glycol, Dimethicone, PEG-30 Dipolyhydroxystearate, Glycerin, Lauryl PEG/PPG-18/18 Methicone, Synthetic Wax, Ammonium Polyacryloyldimethyl Taurate, Caprylyl Glycol, Cellulose Gum, Dimethicone Crosspolymer, Dodecene, Glycine Soja Oil, Isostearyl Alcohol, Pentasodium Ethylenediamine Tetramethylene Phosphonate, Poloxamer 407, Silica, Tocopherol, Triethanolamine. (Code F.I.L.: C171811/1)

 

Anthelios Ultra-Fluid Lotion SPF 60, 50 mL

anthelios-ultra-fluid-50ml

Active Ingredients

Homosalate 10%, Oxybenzone 6%, Octisalate 5%, Octocrylene 5%, Avobenzone 3%, Ecamsule (Mexoryl SX) 2%

Other

Aqua, Cyclopentasiloxane, Alcohol Denat., Cyclohexasiloxane, Styrene/Acrylates Copolymer, Silica, Dicaprylyl Ether, PEG-30 Dipolyhydroxystearate, Dimethicone, Triethanolamine, Glycerin, Nylon-12, Polymethylsilsesquioxane, Caprylyl Glycol, Dicaprylyl Carbonate, Disodium EDTA, Disteardimonium Hectorite, Dodecene, Isostearyl Alcohol, Lauryl PEG/PPG-18/18 Methicone, PEG-8 Laurate, Phenoxyethanol, Poloxamer 407, Poly C10-30 Alkyl Acrylate, Tocopherol. (Code F.I.L.: C182364/1)

 

Anthelios Targeted Protection Stick SPF 60, 9 g

anthelios-stick

Active Ingredients

Octocrylene 10%, Titanium Dioxide 6.25%, Avobenzone 3%, Drometrizole Trisiloxane (Mexoryl XL) 2%

Others

Ricinus Communis, Isopropyl Palmitate, Polyethylene, Isohexadecane, Ozokerite, Theobroma Cacao, Butyrospermum Parkii, Dimethicone, Glycine Soja, Tocopherol. (Code F.I.L. C24262/1C)

 

Anthelios XL Melt-In Cream SPF 60, 100 mL

anthelios-melt-in

Active Ingredients

Octocrylene 10%, Titanium Dioxide 4.15%, Avobenzone 3.5%, Drometrizole Trisiloxane (Mexoryl XL) 3%, Terephthalylidene Dicamphor Sulfonic Acid (Mexoryl SX) 3%

Others

Aqua, Propylene Glycol, Glycerin, Cyclopentasiloxane, Triethanolamine, Isopropyl Palmitate, Stearic Acid, VP/Eicosene Copolymer, Dimethicone, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Aluminum Hydroxide, Carbomer, Disodium EDTA, Glyceryl Stearate, Glycine Soja, Hydroxypropyl Methylcellulose, Methylparaben, PEG-100 Stearate, Phenoxyethanol, Propylparaben, Stearyl Alcohol, Tocopherol. (Code F.I.L.: C15709/2C)

Anthelios XL Melt-In Cream SPF 45, 100 mL

anthelios-melt-in-spf45-jpg

Active Ingredients

Octocrylene 10%, Avobenzone 3.5%, Titanium Dioxide 3.3%, Drometrizole Trisiloxane (Mexoryl XL) 3%, Terephthalylidene Dicamphor Sulfonic Acid (Mexoryl SX) 2%

Others

Aqua, Propylene Glycol, Cyclopentasiloxane, Glycerin, Isopropyl Palmitate, Triethanolamine, Stearic Acid, VP/Eicosene Copolymer, Dimethicone, PEG-100 Stearate, Glyceryl Stearate, Stearyl Alcohol, Phenoxyethanol, Aluminum Hydroxide, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Methylparaben, Carbomer, Hydroxypropyl Methylcellulose, Disodium EDTA, Glycine Soja, Tocopherol, Propylparaben. (Code F.IL.: K17514/3)

Anthelios Lightweight Lotion SPF 60, 100 mL

anthelios-lightweight-spf60

Active Ingredients

Homosalate 10%, Octocrylene 7%, Octisalate 5%, Avobenzone 4%, Drometrizole Trisiloxane (Mexoryl XL) 2.5%, Terephthalylidene Dicamphor Sulfonic Acid (Mexoryl SX) 0.5%

Others

Aqua, Glycerin, Alcohol Denat., Styrene/Acrylates Copolymer, Dimethicone, Propylene Glycol, PEG-100 Stearate, Glyceryl Stearate, Silica, Synthetic Wax, Phenoxyethanol, Sodium Polyacrylate, Triethanolamine, Stearic Acid, Caprylyl Glycol, Palmitic Acid, PEG-8 Laurate, Xanthan Gum, Tocopherol, Disodium EDTA. (Code F.I.L.: K158295/6)

 

Anthelios Lightweight Lotion SPF 30, 100 mL

anthelios-lightweight-spf30

Active Ingredients

Homosalate 10%, Octocrylene 5.5%, Octisalate 5%, Avobenzone 3%, Drometrizole Trisiloxane (Mexoryl XL) 2.5%, Terephthalylidene Dicamphor Sulfonic Acid (Mexoryl SX) 0.5%

Others

Aqua, Glycerin, Alcohol Denat., Styrene/Acrylates Copolymer, Dimethicone, Propylene Glycol, PEG-100 Stearate, Glyceryl Stearate, Silica, Synthetic Wax, Phenoxyethanol, Sodium Polyacrylate, Triethanolamine, Stearic Acid, Caprylyl Glycol, Palmitic Acid, PEG-8 Laurate, Xanthan Gum, Tocopherol, Disodium EDTA. (Code F.I.L.: K158303/4)

 

Anthelios Mineral Tinted Ultra-Fluid Lotion SPF 50, 50 mL

anthelios-mineral-fluid

Active Ingredient

Titanium Dioxide 11%

Non Medicinal Ingredients

Aqua, Isododecane, C12-15 Alkyl Benzoate, Dimethicone, Undecane, Triethylhexanoin, Isohexadecane, Styrene/Acrylates Copolymer, Nylon-12, Caprylyl Methicone, Butyloctyl Salicylate, Phenethyl Benzoate, Silica, Tridecane, Dicaprylyl Carbonate, Dicaprylyl Ether, Talc, Dimethicone/PEG-10/15 Crosspolymer, Aluminum Stearate, Pentylene Glycol, Alumina, Aluminum Hydroxide, Benzoic Acid, C9-15 Fluoroalcohol Phosphate, Caprylyl Glycol, Cassia Alata Leaf Extract, Diethylhexyl Syringylidenemalonate, Disteardimonium Hectorite, CI 77491, CI 77492, CI 77499, Magnesium Sulfate, Maltodextrin, PEG-8 Laurate, PEG-9, PEG-9 Polydimethylsiloxyethyl Dimethicone, Phenoxyethanol, Polyhydroxystearic Acid, Propylene Carbonate, Propylene Glycol, Stearic Acid, Tocopherol. (Code F.I.L.: K50867/4)

 

Anthelios Mist SPF 50, 155 g

anthelios-mist

Active Ingredients

Homosalate 10%, Oxybenzone 6%, Octisalate 5%, Octocrylene 5%, Avobenzone 3%, Ecamsule (Mexoryl SX) 2%

Other

Butane, Aqua, Cyclopentasiloxane, Alcohol Denat., Cyclohexasiloxane, Styrene/Acrylates Copolymer, Silica, Dicaprylyl Ether, PEG-30 Dipolyhydroxystearate, Dimethicone, Caprylyl Glycol, Dicaprylyl Carbonate, Disodium EDTA, Disteardimonium Hectorite, Dodecene, Glycerin, Isostearyl Alcohol, Lauryl PEG/PPG-18/18 Methicone, Nylon-12, PEG-8 Laurate, Phenoxyethanol, Poloxamer 407, Poly C10-30 Alkyl Acrylate, Polymethylsilsesquioxane, Tocopherol, Triethanolamine. (Code F.I.L. C182096/1)

“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
Octocrylene
Avobenzone
Octinoxate
Octisalate
Oxybenzone
Homosalate
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.

ptabletizno

 

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.

avobenzone

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.

uv-color-spectrum

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.