Specific Extinction Spectra Of Sunscreen Filters

It is not uncommon to read that a specific filter is a blocker of a specific type of UV radiation. Indeed, most sources which provide information on cosmetics have a system of symbols which represents how well different filters block different types of radiation.

For example, on websites and databases which function to explain the function of cosmetic ingredients, one often sees systems like this:

Sunscreen UV Protection.png

I understand why filters are presented like this. It is good shorthand. I also take real umbrage with it. In that it is shorthand, it is reductive. The reality is about one trillion times more complex. My issues can be summarized:

  1. It presents UV radiation as a “Yes” or “No”for each category of wavelength. If a filter is said to filter UVB, one would be led to incorrectly assume that the filter offers a consistent level of UV extinction through the 30 individual wavelength of UVB. This is literally never the case with sunscreen ingredients. UV is a spectrum, and each wavelength of UV light delivers a unique amount of energy. The molecular composition of different sunscreen filters cause each filter to respond to different wavelengths of radiation differently.

  2. It provides no context for how efficient the UV filter is for each “category” of UV light. This is quite an issue. Some filters are much more absorptive than others. As in, to get any real protection from Meridamate, one needs to use a much higher quantity of it than one does Avobenzone.

The best way to understand the actual absorbing capability of a sunscreen filter is by looking at its specific extinction, which I’ve attempted to explain in the context of sunscreens here.

I will summarize briefly: specific extinction refers to the sunscreen ingredient’s absorbance in accordance with a fixed set of parameters: how much of each wavelength is made extinct through a 1cm long 1% concentration of the solubilized filter. Looking at specific extinction spectra provide a facile way to compare the effectiveness of isolated sunscreen filters. One can compare “apples to apples”: how well one filter did versus another, in accordance with the same set of parameters. Looking at a filter’s specific extinction allows one to determine which wavelengths it filters effectively, and the rate of that efficacy per filter.

It is worth stating that looking at the specific extinction of a filter will not give an absolute indication of how well the filter will perform in an actual sunscreen product. In real life, there are a myriad of other factors which will impact the protection of a sunscreen beyond the absorptive capability of the filters. Below is an incomplete list of things which can impact the actual absorbance of a sunscreen formula

  1. The vehicle cream
  2. Synergistic or photodegratory interactions between sunscreen filters
  3. The concentration at which the sunscreen filter is included in a product
  4. The filter’s photostability, and the rate of its potential degradation given the ambient UV in one’s environment
  5. Whether or not the filters are encapsulated, and if so, the encapsulation technology
  6. The concentration of emollients / antioxidants / other ingredients which impact the performance of the sunscreen filters

However, if one wants to look at the actual performance of a sunscreen formula – not a specific active ingredient – one must measure absorbance. Like specific extinction, Absorbance measures how much of the UV light failed to get from the start of a system to the end, but it allows for testing of sunscreen at the indicated dosage form, which Specific Extinction, obviously, does not.

That said, let’s look at the filters.

Broad Spectrum Filters

Bemotrizinol; Tinosorb S (BASF); Parsol Shield (DSM); INCI: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine

Bemotrizinol; Tinosorb S (BASF); Parsol Shield (DSM); INCI: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine

INCI: Tris-Biphenyl Triazine (nano); Tinosorb A2B (nano) (BASF)

INCI: Tris-Biphenyl Triazine (nano); Tinosorb A2B (nano) (BASF)

Bisoctrizole; Tinosorb M (BASF); Parsol Max (DSM); INCI: Methylene Bis-Benzotriazolyl Tetramethylbutylphenol

Bisoctrizole; Tinosorb M (BASF); Parsol Max (DSM); INCI: Methylene Bis-Benzotriazolyl Tetramethylbutylphenol

INCI: Drometrizole Trisiloxane; Mexoryl XL (L’Oréal)

INCI: Drometrizole Trisiloxane; Mexoryl XL (L’Oréal)

Zinc Oxide

Zinc Oxide

All of them!

All of them!

UVA Filters

Avobenzone; INCI: Butyl Methoxydibenzoylmethane

Avobenzone; INCI: Butyl Methoxydibenzoylmethane

DHHB; Uvinul A Plus (BASF); INCI: Diethylamino Hydroxybenzoyl Hexyl Benzoate

DHHB; Uvinul A Plus (BASF); INCI: Diethylamino Hydroxybenzoyl Hexyl Benzoate

Ecamsule; Mexoryl SX (L’Oréal); INCI: Terephthalylidene Dicamphor Sulfonic Acid

Ecamsule; Mexoryl SX (L’Oréal); INCI: Terephthalylidene Dicamphor Sulfonic Acid

Bidisulizole Disodium; Neo Heliopan AP (Symrise); INCI: Disodium Phenyl Dibenzimidazole Tetrasulfonate

Bidisulizole Disodium; Neo Heliopan AP (Symrise); INCI: Disodium Phenyl Dibenzimidazole Tetrasulfonate

Meridamate; INCI: Menthyl Anthranilate

Meridamate; INCI: Menthyl Anthranilate

All of them!

All of them!

Solid UVB & UVA II Filters

INCI: Ethylhexyl Triazone; Octyl Triazone; Uvinul T 150 (BASF)

INCI: Ethylhexyl Triazone; Octyl Triazone; Uvinul T 150 (BASF)

Iscotrizinol; INCI: Diethylhexyl Butamido Triazone; Uvasorb HEB (3V Sigma)

Iscotrizinol; INCI: Diethylhexyl Butamido Triazone; Uvasorb HEB (3V Sigma)

Enzacamene; INCI: 4-Methylbenzylidene Camphor

Enzacamene; INCI: 4-Methylbenzylidene Camphor

Ensulizole; INCI: Phenylbenzimidazole Sulfonic Acid

Ensulizole; INCI: Phenylbenzimidazole Sulfonic Acid

Titanium Dioxide

Titanium Dioxide

Oxybenzone; INCI: Benzophenone-3

Oxybenzone; INCI: Benzophenone-3

Sulisobenzone; INCI: Benzophenone-4

Sulisobenzone; INCI: Benzophenone-4

All of them!

All of them!

Liquid UVB & UVA II Filters

Padimate-O; INCI: 2-Ethylhexyl Dimethyl PABA

Padimate-O; INCI: 2-Ethylhexyl Dimethyl PABA

Amiloxate; INCI: Isoamyl p-Methoxycinnamate

Amiloxate; INCI: Isoamyl p-Methoxycinnamate

Octinoxate; INCI: Ethylhexyl Methoxycinnamate

Octinoxate; INCI: Ethylhexyl Methoxycinnamate

Octocrylene

Octocrylene

Octisalate (or Octyl Salicylate); INCI: Ethylhexyl Salicylate

Octisalate (or Octyl Salicylate); INCI: Ethylhexyl Salicylate

Polysilicone-15; Parsol SLX (DSM)

Polysilicone-15; Parsol SLX (DSM)

Homosalate (or Homomethyl Salicylate)

Homosalate (or Homomethyl Salicylate)

All of them!

All of them!

Please be adivsed I have left off several filters which I have literally never seen in sunscreen products. They include Dioxybenzone, Cinoxate, PABA, Trolamine Salicylate, several more. These don't really play a role in sun protecting products as sold to consumers.

Note: I originally listed the regulatory allowance of each filter in this post. I have since done a better job of listing these regulations in this post.

Cited

Extinction Spectra from:

Osterwalder, U., & Herzog, B. (2009). Chemistry and Properties of Organic and Inorganic UV Filters. In Editor H. W. Lim & Z. D. Draelos (Eds.), Clinical Guide to Sunscreens and Photoprotection (pp. 33). New York, NY: Informa Healthcare USA, Inc

& BASF Care Creations

Sunscreen Regulations:

Australia | Canada | Europe | Japan & Japan (again) | United States