Sunscreen Formula for Sensitive, Acne-Prone Skin

Is Silicone Necessary?

For a sunscreen using physical filters like Titanium Dioxide and Zinc Oxide, silicones are often included in the liquid dispersions of these minerals. Products like Titanium Dioxide 15nm Liquid (Gloss) and Zinc Oxide 35nm Liquid already contain silicones (such as Cyclomethicone and Dimethicone) as part of their base. These silicones help to evenly disperse the mineral particles, improve the texture, spreadability, and contribute to the water resistance of the sunscreen.

While it is possible to create a physical sunscreen without silicones, the liquid forms you are using are designed to work with them. Adding additional silicones beyond what is already in these liquid dispersions is not strictly necessary for sun protection and may alter the feel or compatibility of the formula. For sensitive and acne-prone skin, minimizing unnecessary ingredients is often beneficial. Silicones used in these types of dispersions are generally considered non-comedogenic and suitable for sensitive skin.

Evaluation of Your Proposed Formula

Your formula uses excellent choices for active ingredients and a preservative suitable for sensitive skin:

• Aloe Vera Gel (Heavy): This is a gentle, oil-free base suitable for sensitive and oily/dehydrated skin.
• Titanium Dioxide 15nm Liquid (Gloss) and Zinc Oxide 35nm Liquid: These are physical sunscreen filters that provide broad-spectrum protection (UVA/UVB) and are generally well-tolerated by sensitive skin. They are also described as lightweight and non-clogging.
• Mild Preserved Eco: This preservative is gentle and suitable for sensitive skin.

However, there is a potential compatibility issue with the proposed formula structure:

• The Titanium Dioxide 15nm Liquid (Gloss) and Zinc Oxide 35nm Liquid products are specifically developed for use in water-in-oil emulsion systems.
• Your formula uses a high percentage (59%) of Aloe Vera Gel (Heavy), which is a water-based gel.
• Mixing a large amount of a water-based gel with ingredients designed for water-in-oil emulsions may lead to instability, poor dispersion of the UV filters, and potentially reduced sun protection effectiveness. The descriptions for the liquid sunscreen actives explicitly state they are "not recommended for use in an oil-in-water emulsion system" (and a gel is essentially a high-water content system).

Conclusion: While the individual ingredients are good choices for sensitive, acne-prone skin, this specific combination and ratio of a high-percentage water-based gel with sunscreen actives designed for water-in-oil emulsions is unlikely to be stable or provide optimal sun protection. It would be more effective to formulate a water-in-oil emulsion following the recommendations for the Titanium Dioxide 15nm Liquid (Gloss) and Zinc Oxide 35nm Liquid, using an appropriate oil or silicone phase and emulsifier for a water-in-oil system, rather than mixing them into a pre-made gel base.