UV Filters in Sun Care Market

Inorganic sunscreens Strengths & Weaknesses

Strengths	Weaknesses
Safe / non-irritant	Perception of poor aesthetics (skinfeel and whitening on skin)
Broad spectrum	Powders can be difficult to formulate with
High SPF (30+) can be achieved with a single active (TiO2)	Inorganics have been caught up in the nano debate
Dispersions are easy to incorporate
Photostable

Inorganic Sunscreens Applications
Inorganic sunscreens are suitable for any UV protection applications except clear formulations or aerosol sprays. They are particularly well suited for baby sun care, sensitive skin products, products making “natural” claims, and decorative cosmetics.
Inorganic UV filters Chemical Types

Titanium Dioxide
• Primarily a UVB filter, but some grades also provide good UVA protection
• Various grades available with different particle sizes, coatings etc.
• Most grades fall into the realm of nanoparticles
• Smallest particle sizes are very transparent on skin but give little UVA protection; larger sizes give more UVA protection but are more whitening on skin

Zinc Oxide
• Primarily a UVA filter; lower SPF efficacy than TiO2, but gives better protection than TiO2 in the long wavelength “UVA-I” region
• Various grades available with different particle sizes, coatings etc.
• Most grades fall into the realm of nanoparticles

Performance / Chemistry matrix

Rate from -5 to +5:
-5: significant negative effect | 0: no effect | +5: significant positive effect
(Note: for cost and whitening, “negative effect” means cost or whitening is increased.)

	Cost	SPF	UVA Protection	Skin Feel	Whitening	Photo-stability	Water Resistance
Benzophenone-3	-2	+4	+2	0	0	+3	0
Benzophenone-4	-2	+2	+2	0	0	+3	0
Bis-ethylhexyloxyphenol Methoxyphenyl Triazine	-4	+5	+5	0	0	+4	0
Butyl Methoxy-dibenzoylmethane	-2	+2	+5	0	0	-5	0
Diethylamino Hydroxy Benzoyl Hexyl Benzoate	-4	+1	+5	0	0	+4	0
Diethylhexyl Butamido Triazone	-4	+4	0	0	0	+4	0
Disodium Phenyl Dibenzimiazole Tetrasulfonate	-4	+3	+5	0	0	+3	-2
Ethylhexyl Dimethyl PABA	-1	+4	0	0	0	+2	0
Ethylhexyl Methoxycinnamate	-2	+4	+1	-1	0	-3	+1
Ethylhexyl Salicylate	-1	+1	0	0	0	+2	0
Ethylhexyl Triazone	-3	+4	0	0	0	+4	0
Homosalate	-1	+1	0	0	0	+2	0
Isoamyl p-Methoxycinnamate	-3	+4	+1	-1	0	-2	+1
Menthyl Anthranilate	-3	+1	+2	0	0	-1	0
4-Methylbenzylidene Camphor	-3	+3	0	0	0	-1	0
Methylene Bis-Benzotriazolyl Tetramethylbutylphenol	-5	+4	+5	-1	-2	+4	-1
Octocrylene	-3	+3	+1	-2	0	+5	0
Phenylbenzimidazole Sulfonic Acid	-2	+4	0	0	0	+3	-2
Polysilicone-15	-4	+1	0	+1	0	+3	+2
Tris-biphenyl Triazine	-5	+5	+3	-1	-2	+3	-1
Titanium Dioxide – transparent grade	-3	+5	+2	-1	0	+4	0
Titanium Dioxide – broad spectrum grade	-3	+5	+4	-2	-3	+4	0
Zinc Oxide	-3	+2	+4	-2	-1	+4	0

Factors Impacting Performance of UV Filters

Performance attributes of titanium dioxide and zinc oxide vary considerably depending on the individual properties of the specific grade used, eg. coating, physical form (powder, oil-based dispersion, water-based dispersion). Users should consult with suppliers before selecting the most appropriate grade to meet their performance objectives in their formulation system.

The efficacy of oil-soluble organic UV filters is influenced by their solubility in the emollients used in the formulation. Generally, polar emollients are the best solvents for organic filters.

The performance of all UV filters is critically influenced by the rheological behavior of the formulation and its ability to form an even, coherent film on the skin. The use of suitable film-formers and rheological additives often helps to improve the efficacy of the filters.
Interesting Combination of UV filters (synergies)

There are many combinations of UV filters that show synergies. The best synergistic effects are usually achieved by combining filters that complement each other in some way, for example:-
• Combining oil-soluble (or oil-dispersed) filters with water-soluble (or water-dispersed) filters
• Combining UVA filters with UVB filters
• Combining inorganic filters with organic filters

There are also certain combinations that can yield other benefits, for example it is well known that octocrylene helps to photo-stabilize certain photo-labile filters such as butyl methoxydibenzoylmethane.

However one must always be mindful of intellectual property in this area. There are many patents covering particular combinations of UV filters and formulators are advised to always check that the combination they intend to use does not infringe any third-party patents.

Select the Right UV filter for your Cosmetic Formulation

The following steps will help you select the right UV filter(s) for your cosmetic formulation:
1. Set out clear objectives for the performance, aesthetic properties and intended claims for the formulation.
2. Check which filters are permitted for the intended market.
3. If you have a specific formulation chassis that you wish to use, consider which filters will fit with that chassis. However if possible it is best to choose the filters first and design the formulation around them. This is especially true with inorganic or particulate organic filters.
4. Use advice from suppliers and/or prediction tools such as the BASF Sunscreen Simulator to identify combinations that should achieve the intended SPF and UVA targets.

These combinations can then be tried in formulations. In-vitro SPF and UVA testing methods are useful at this stage to indicate which combinations give the best results in terms of performance - more information on the application, interpretation and limitations of these tests can be gathered with the SpecialChem e-training course: UVA/SPF: Optimizing your Test Protocols

The test results, along with the results of other tests and assessments (eg. stability, preservative efficacy, skin feel), enable the formulator to select the best option(s) and also guide the further development of the formulation(s).