Developing superior sun care products (EU) is one of the most challenging areas in personal care formulation. Sun care accounted for 10% of the global skincare market in 2013 and is expected to grow 6.5% annually from 2013 to 2017. Research shows consumers are highly concerned about sun damage with 62% seeking sun protection benefits in skin and body care products.
Sun care formulations can be broken down into two general categories: daily wear SPF and recreational products intended for the beach. Best in class sunscreen formulations from major personal care companies use approximately 6% active for an SPF of 30 for metal oxide-based sunscreens and 9% for chemical sunscreens.
Daily wear SPF moisturizers are intended for the face and are required to be formulated differently than beach products. Daily wear products need to absorb quickly, be non-greasy, and non-irritating. The product film also needs to resist migration over time caused by skin oil production.
SPF 30 daily wear products have become the norm and these formulations typically contain an average of 19% sunscreen or an efficiency of 1.6 SPF units / 1% sunscreen. This makes it challenging to get good skin feel while minimizing skin irritation due to the high level of sunscreens used, which can additionally contribute to greasy skin feel. Using metal oxide based sunscreens like titanium dioxide (EU) or zinc oxide (EU) can help increase SPF efficiency and reduce irritation. They can sometimes cause whitening and a dry skin feel when using over 3%.
Formulating metal oxides into a water-in-oil emulsion can help reduce the dry skin feel. Metal oxides cannot, however, be used with avobenzone (EU) in the U.S., making it more difficult to achieve a high SPF with good skin feel using only metal oxides. The best strategy is to increase the SPF efficiency to at least 3-5 SPF units / 1% sunscreen using Octinoxate (EU) / Zinc Oxide, Octinoxate / Octocrylene (EU) / Avobenzone as primary sunscreens with SPF-boosting technology. Many SPF boosters can also reduce sunscreen skin penetration and improve sweat resistance.
SPF boosters typically work by:
- Increasing the viscosity and changing the rheological properties (shear thinning) of the sunscreen film on skin.
- Increasing the photo stability of unstable sunscreens.
- Increasing sunscreen uniformity and film thickness on skin.
- Reducing sunscreen film migration on skin over time.
- Absorbing UV / increasing UV light scattering.
- Shifting the UV absorption max to a higher wavelength.
When using Avobenzone, you need to make certain that it is properly solubilized and won’t crystallize. Using a chelator and a non-formaldehyde-donating preservative is also critical to maintain avobenzone stability.
Recreational suncare products are designed to be used on the beach to prevent skin burning and redness. The products need to be easily applied and provide a high level of wash, sweat, and rub resistance. The typical recreational sunscreen product is a spray form, has an SPF of 30+, and normally contains 2-3% water proofing polymer.
The best technical rationale in formulating SPFs of greater than 30 is that under normal use conditions most people only apply around .5-1mg / cm2 of product and SPF testing is performed using 2mg / cm2 of product. This means that the SPF under normal use conditions is approximately 2-4 times lower than the claimed SPF.
The future direction in sunscreen formulation will most likely involve improving SPF efficiency and reducing sunscreen skin penetration using globally approved actives. Novel active delivery systems and formulation approaches will be critical in achieving this.
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