The sun care market is rapidly expanding. As awareness about UV protection grows, the market value of the global sunscreen industry also expects significant growth in 2024 and beyond for beauty and personal care. However, modern consumers demand more than just the standard sun protection factor (SPF). They seek hybrid skin and sun care products that integrate seamlessly into their everyday beauty routines. Brightening specialties are a leading sector in sun care, followed by acne treatment, anti-aging products, and skincare sets. This shift drives innovation in sunscreen formulations – particularly in developing powder SPF products.

Sunscreen: A year-round essential product

Today's advanced sunscreen formulations cater to various skin tones and needs, featuring benefits like moisturization and vegan ingredients. As consumers educate themselves about ingredients used in sunscreen, brand transparency has become more crucial to helping consumers select their sun care products. Applying sunscreen is no longer just a seasonal necessity but an integral part of daily skincare. Sun protection products provide a barrier against UV damage and promote overall skin health throughout the year.

For consumers looking to use sunscreen year-round, products come in various innovative formats, including creams, lotions, sprays, gels, sticks, and powders. This variety of sunscreen formats allows consumers to choose the best option for their lifestyle. Innovative claims such as broad-spectrum protection, blue light defense, anti-pollution, and infrared protection are becoming more common as consumers seek comprehensive UV protection solutions.

The powder SPF market is growing due to its convenience and versatility. Powder sunscreens offer easy application without disrupting makeup, making them ideal for daily touch-ups. These products typically contain mineral sunscreen ingredients like zinc oxide and titanium dioxide. Popular types of powder SPF include:

• Brush-on Powders: Loose or pressed powders with built-in brushes for easy application
  Powder Sunscreen with Applicator Pads: Soft applicator pads or puffs distribute the powder evenly
• Colored or Tinted Powders: Provide sun protection and a touch of color to even out skin tone
• Translucent Powders: Control shine and set makeup while offering SPF protection
• Hair and Scalp Powders: Protect the scalp and hair from UV rays
• Powder Sunscreen with Blotting Paper: Combine oil-absorbing blotting paper with SPF protection
• Hybrid Products: Combine powder sunscreen with skincare benefits like antioxidants and hydration

Substantiating sun protection claims through testing is essential. However, testing powder products presents unique challenges due to their weak adhesive properties and static-induced scattering.

Traditional in vivo testing can be costly, variable, and potentially harmful to participants. In vitro testing allows manufacturers to assess a product's initial effectiveness before proceeding to human trials.

Additionally, in vitro testing helps manufacturers determine the appropriate formulation and concentration of sunscreen ingredients to achieve the desired SPF level. It helps to narrow down the list of potential sunscreen candidates for further evaluation. Products with low efficacy in vitro may not proceed to costly and time-consuming in vivo testing. In vitro testing best supports new sunscreen formulations and innovative delivery methods such as powders or sprays.

It is important to note that while in vitro testing provides valuable data on a product's UV-blocking capabilities, it does not fully replicate the complexity of interactions when sunscreen is applied to human skin. Factors like skin's natural oils, sweat, and other environmental conditions can affect real-world effectiveness. Thus, in vitro results are often complemented by in vivo (human-based) testing to provide a more comprehensive understanding of the product's performance. 

I+S from Univar Solutions has developed an in vitro SPF testing methodology tailored to suit powder products. The process involves applying a solvent (C12-C15 alkyl benzoate) to a polymethyl methacrylate (PMMA) substrate to improve powder adhesion, followed by even distribution of the powder using a sieve to avoid the formation of clumps. Then, the mixture of powder and solvent was spread homogeneously on the PMMA plate. The SPF value was measured using spectrophotometer equipment. SPF results demonstrated that by sprinkling the powder after applying the solvent, the SPF values were more accurate, and the standard deviation was minimized.

SPF analysis was simulated in vitro following a modified method for powders of the lab's internal standard operating procedure, which used the following parameters:

• Substrate: HelioPlate HD6 PMMA plates
• Sunscreen application: 2 mg/cm2 powder and 1 mg/cm2 of solvent using an analytical balance
• 1 mg/cm2 of C12-15 Alkyl Benzoate solvent was applied to the HelioPlate and spread evenly
• Sunscreen was premixed immediately before sampling for application
• Sunscreen was dusted over the prepared plate and rubbed in to create an even mixture
• Three test substrates per sunscreen
• Instrument: Optometrics (now Solar Light) SPF-290AS automated sunscreen analyzer
• 9 SPF readings per substrate (reported as an average of nine readings and the standard deviation)
• SPF standard: FDA SPF Standard/P2 High SPF Standard, Lot# 1902AB (Solar Light Company)
• Static SPF measured 15 minutes post-application

Key Findings and Method Development

• Solvent Application: Applying C12-C15 alkyl benzoate to the PMMA plate before powder application improved reproducibility and minimized standard deviation in SPF values.
• Powder Distribution: Using a sieve to distribute the powder evenly prevented clumping and ensured consistent results.
• SPF Accuracy: The developed method yielded SPF values that closely matched label claims, demonstrating the method's effectiveness.

Formulating a sunscreen that meets the producer's desired requirements while maintaining good skin feel, performance, and stability can be challenging. Therefore, it's important to consider and carefully choose the types of ingredients used in the sunscreen formula and understand how ingredient quality and proportions can impact the desired SPF value, performance, and stability. Powder sunscreens are gaining popularity, and robust in vitro testing is crucial for validating their performance.

Our method development highlights the importance of precise solvent-to-powder ratios and thorough testing to ensure product efficacy. While in vivo testing minimizes the ethical concerns associated with human testing and is valuable, it should be complemented by in vivo testing to confirm real-world performance testing. This combination of testing approaches ensures a comprehensive evaluation of sunscreen efficacy and safety.