How to Formulate Effective Mineral Sunscreens: A Comprehensive Guide for Cosmetic Formulators

Wearing sunscreen is essential for maintaining healthy skin, preventing skin cancer, and avoiding premature aging. The sun care market continues to lead the way as one of the fastest growing categories of skin care. This is primarily driven by increasing consumer awareness on the impact and damage that the sun can have on unprotected skin. According to Statista, the global market for sun care products was valued at over $13 billion in 2019 and is expected to reach $27 billion by 2029.

Due to the vast number of sunscreen products available, consumers have become more discerning in their choices. They now expect sun protection to be incorporated into their daily beauty routines, including hair care and lip care products.

The green beauty movement has heightened awareness about the issues with chemical-based sunscreens. There are ongoing concerns about the safety of certain ingredients and their environmental impact, such as harmful effects on marine life.

Consequently, many traditional sunscreen ingredients are being reconsidered, leading to a trend towards mineral-based sunscreens. These products are preferred by eco-conscious consumers for their perceived safety, sustainability, and environmental friendliness. However, formulating effective mineral-based sunscreens presents its own unique challenges. Continue reading to find out what makes a mineral-based sunscreen effective.

How Sunscreen Works

Understanding the mechanisms behind sunscreen is crucial for creating effective sun care products. Sunscreen serves as a barrier that protects the skin from harmful ultraviolet (UV) radiation, thereby preventing sunburn, skin cancer, and premature aging. Here’s an in-depth look at how sunscreens function and what formulators need to consider.

Types of UV Radiation

  • UVA Rays: Penetrate deep into the dermis, leading to premature aging and wrinkles. They also contribute to skin cancer development.
  • UVB Rays: Affect the outer skin layer, causing sunburn and playing a significant role in skin cancer.
  • UVC Rays: Absorbed by the Earth's atmosphere and do not reach the ground, thus not a concern for skin exposure.

Mechanisms of Sunscreen

  1. Chemical Sunscreen
    • Active Ingredients: Commonly include organic compounds like oxybenzone, avobenzone, octocrylene, and homosalate.
    • Mechanism: These compounds absorb UV radiation and convert it into heat, which is then released from the skin. This prevents the UV rays from penetrating and causing cellular damage.
    • Formulation Tips: Ensure adequate photostability and consider the synergy between different UV filters to achieve broad-spectrum protection. Pay attention to ingredient compatibility and potential skin sensitization.
  2. Mineral Sunscreen
    • Active Ingredients: Typically use inorganic compounds such as zinc oxide and titanium dioxide.
    • Mechanism: Acts as physical blockers by sitting on the skin’s surface and reflecting or scattering UV radiation. They provide immediate protection upon application.
    • Formulation Tips: Focus on particle size to minimize the white cast while maintaining efficacy. Consider the dispersion of these particles within the formulation to ensure uniform protection.

Broad Spectrum Protection

  • Broad-Spectrum: Formulations should protect against both UVA and UVB rays. This is achieved by combining ingredients that cover the entire UV spectrum.

Sun Protection Factor (SPF)

  • SPF Rating: Indicates the level of protection against UVB rays. For instance, an SPF 30 means the skin can be exposed to UVB rays 30 times longer than without protection.
  • Formulation Considerations: Balance SPF with aesthetic and sensory attributes. Higher SPF often requires higher concentrations of active ingredients, which can affect the product’s feel and appearance.

Formulation Strategies

  • Synergy of Ingredients: Combine multiple UV filters to enhance efficacy and achieve desired SPF levels while maintaining a pleasant sensory profile.
  • Photostability: Ensure that the chosen ingredients remain stable and effective under UV exposure.
  • Skin Compatibility: Select ingredients that are non-irritating and suitable for various skin types, including sensitive skin.

Application and Reapplication Guidelines

  • Effective Coverage: Advise users to apply a generous amount of sunscreen to all exposed areas. For formulators, this means creating products that spread easily and are pleasant to apply.
  • Reapplication: Emphasize the importance of reapplying sunscreen every two hours, especially after swimming, sweating, or toweling off. Formulate products that encourage frequent use through ease of application and comfort on the skin.

By understanding these mechanisms and considerations, cosmetic formulators can develop sunscreens that provide effective protection while meeting consumer expectations for safety, sustainability, and sensory experience.

How to Formulate Mineral Sunscreens

Formulating mineral sunscreens involves a delicate balance of selecting the right active ingredients, ensuring effective protection, and achieving a desirable sensory profile. Here’s a comprehensive guide to help cosmetic formulators create high-performing mineral sunscreens.

Key Active Ingredients

  • Zinc Oxide: Offers broad-spectrum protection by reflecting and scattering both UVA and UVB rays. It's non-irritating and suitable for sensitive skin.
  • Titanium Dioxide: Provides excellent UVB and partial UVA protection. It’s often used in combination with zinc oxide for enhanced efficacy.

Formulation Steps

  1. Choosing the Right Base
    • Emollients: Select lightweight, non-comedogenic emollients like GreenDiol or caprylic/capric triglyceride to improve spreadability and skin feel.
    • Humectants: Incorporate humectants like glycerin or hyaluronic acid to maintain skin hydration and enhance the formula’s moisturizing properties.
  2. Dispersion of Mineral Filters
    • Particle Size: Use micronized or nano-sized particles to reduce the white cast while ensuring effective UV protection. Ensure compliance with regulatory guidelines regarding particle size.
    • Even Distribution: Achieve uniform dispersion of zinc oxide and titanium dioxide by using high-shear mixing and appropriate dispersing agents like lecithin or polysorbate.
  3. Stabilizing the Formula
    • Thickeners and Stabilizers: Add thickeners like xanthan gum or carbomer to achieve the desired viscosity and stability. Consider using stabilizers like magnesium sulfate to prevent settling and improve suspension.
    • Antioxidants: Include antioxidants such as vitamin E (tocopherol) or green tea extract to enhance the formula’s stability and provide additional skin benefits.
  4. Enhancing Aesthetic and Sensory Attributes
    • Sensory Enhancers: Use sensory modifiers like silicones (e.g., dimethicone) or esters (e.g., isopropyl myristate) to improve the texture and skin feel.
    • Tinting Agents: Incorporate iron oxides to provide a natural tint, which helps to blend the white cast and offer a more cosmetically elegant finish.
  5. Ensuring Efficacy and Safety
    • SPF Testing: Conduct in-vitro and in-vivo SPF testing to verify the sunscreen’s effectiveness and ensure it meets the desired protection levels.
    • Photostability: Test the photostability of the formula to ensure that the UV filters remain effective after exposure to sunlight.
    • Skin Compatibility: Perform dermatological testing to confirm the product is non-irritating and suitable for sensitive skin.

What Makes an Effective Sunscreen?

Creating an effective sunscreen involves more than just selecting UV filters. It requires a thoughtful approach to formulation, ensuring that the product provides reliable protection while also being user-friendly and cosmetically elegant. Here are the key factors that contribute to a more effective sunscreen:

Broad-Spectrum Protection

  • UVA and UVB Coverage: An effective sunscreen must protect against both UVA and UVB rays. UVA rays penetrate deep into the skin, causing aging and contributing to skin cancer, while UVB rays cause sunburn and also play a role in skin cancer. Ensure your sunscreen offers broad-spectrum protection, which is typically indicated on the product label.

Adequate SPF

  • Sun Protection Factor (SPF): The SPF rating indicates the level of protection against UVB rays. Higher SPF values provide greater protection. For everyday use, an SPF of at least 30 is recommended, while SPF 50+ is advisable for extended outdoor activities. It's crucial to test the SPF in both in-vitro and in-vivo conditions to confirm the claimed protection level.

Photostability

  • Stability Under Sunlight: The active ingredients in sunscreen must remain effective when exposed to sunlight. Photostability ensures that the UV filters do not degrade, maintaining their protective capabilities throughout sun exposure. Combining photostable ingredients and incorporating antioxidants can enhance the formula's stability.

Uniform Coverage

  • Even Application: For sunscreen to be effective, it must be evenly applied to the skin. The formulation should spread easily and form a uniform film on the skin surface. Using lightweight emollients and film-forming agents can help achieve this.

Water and Sweat Resistance

  • Durability: Sunscreens that offer water and sweat resistance are more effective for active users. This feature ensures the product remains on the skin and continues to provide protection during swimming or sweating. Formulators should conduct water resistance testing and clearly indicate the duration of water resistance on the product label.

Sensory and Aesthetic Qualities

  • User Experience: A sunscreen that feels good on the skin is more likely to be used consistently. Focus on creating a non-greasy, lightweight formula that absorbs quickly and leaves a pleasant finish. Adding sensory modifiers like silicones or esters can improve the product's feel and appearance.
  • Cosmetic Elegance: Addressing the issue of white cast, particularly in mineral sunscreens, is essential. Using micronized or coated mineral particles and incorporating tinting agents can help create a more cosmetically elegant product that blends seamlessly with various skin tones.

Ingredient Synergy

  • Combining UV Filters: Using a combination of UV filters can provide comprehensive protection and enhance the formula's efficacy. For example, combining zinc oxide with titanium dioxide in mineral sunscreens or blending different chemical filters can ensure broad-spectrum coverage and improve photostability.

Skin-Friendly Formulation

  • Minimal Irritation: Choose ingredients that are gentle and non-irritating, especially for sensitive skin. Avoid potential allergens and irritants, and consider hypoallergenic and dermatologist-tested claims to appeal to sensitive skin consumers.
  • Moisturizing and Protective: Incorporating hydrating ingredients like glycerin, hyaluronic acid, and natural oils can provide additional skin benefits, making the sunscreen more appealing for daily use.

Compliance with Regulations

  • Safety and Efficacy Standards: Ensure the sunscreen complies with relevant regulatory standards and guidelines in the markets where it will be sold. This includes proper labeling, stability testing, and adhering to approved ingredient lists and concentrations.

By focusing on these factors, formulators can create sunscreens that not only provide effective protection against UV radiation but also meet consumer demands for performance, comfort, and safety.

Formulating effective mineral sunscreens requires a nuanced understanding of UV protection, ingredient synergy, and consumer preferences. By incorporating essential UV filters like zinc oxide and titanium dioxide, leveraging the benefits of SPF boosters, and ensuring broad-spectrum coverage, formulators can create sunscreens that offer robust protection and a pleasant user experience. Additionally, focusing on photostability, even application, and skin-friendly ingredients ensures the sunscreen is not only effective but also enjoyable to use. As consumers become more discerning and eco-conscious, developing mineral sunscreens that balance efficacy, aesthetics, and sustainability will continue to be a critical and rewarding challenge for cosmetic formulators. With the right approach, you can create sun care products that meet the highest standards of protection and performance, ensuring your customers stay safe and satisfied under the sun.