Sunscreen Lotion Formulation Feedback

Regarding your proposed lotion sunscreen formula and questions:

• Adding Fragrance Oil: Yes, fragrance oil can be added to a lotion formula. It is best to first dissolve the fragrance oil in an oil or solvent like Dipropylene Glycol (which is already in your formula) and then add this mixture towards the end of the formulation process. This should be done after the main emulsion has formed and cooled down to help preserve the volatile fragrance compounds.

• Using a Preservative: Yes, it is necessary to include a preservative in a lotion formula containing water to prevent microbial growth. Phenoxyethanol SA is a suitable broad-spectrum preservative for cosmetic lotions. The recommended usage rate for Phenoxyethanol SA is typically 0.5-1.25%. It should be added in the final step of your formulation process, when the temperature of the mixture is below 60°C and the pH is between 2.0-6.0.

• Reviewing Your Proposed Formula:

  • The percentage of Fragrance Oil you included (15%) is very high for a lotion applied to the skin. High concentrations of fragrance can cause skin irritation. Fragrance is typically used at much lower levels in skincare, usually between 0.1% and 1%, and rarely exceeding 5%. We strongly recommend significantly reducing the amount of fragrance oil in your formula.
  • The percentage of Dipropylene Glycol (15%) is also quite high. While it serves as a good solvent for fragrance, this amount might affect the final texture and feel of your lotion.
  • The total percentage of the ingredients in your formula adds up to 115%, which is incorrect. The percentages of all ingredients in a formulation must add up to exactly 100%.
  • Your formula combines water, oils (Fractionated Coconut Oil), and physical sunscreen dispersions (Titanium Dioxide 15nm Liquid, Zinc Oxide 35nm Liquid). The liquid forms of Titanium Dioxide and Zinc Oxide you selected are designed for water-in-oil emulsions and contain their own dispersants/emulsifiers. Pro Polymer is a water-phase thickener. Creating a stable lotion with this combination of ingredients and phases might be challenging and typically requires a carefully selected and balanced emulsification system designed for physical sunscreens.

We recommend referring to tested sample formulations, such as the "Water Resistant Physical Sunscreen" recipe that the staff linked previously. These recipes provide proven ratios and methods for successfully creating stable and effective physical sunscreen lotions, which can serve as a better starting point for your formulation.

By starting with a tested base formula and adjusting the fragrance level to a much lower, safer percentage (dissolving it in a suitable solvent like Dipropylene Glycol before adding), you can create a stable and pleasant-smelling sunscreen lotion.