Impact of Adding Glycerin and Water Film to Sunscreen Serum

Adding ingredients to a sunscreen formulation, even in small amounts, can technically affect the final SPF and PA values. This is because the overall composition influences how the UV filters are dispersed and how the product forms a film on the skin, which are critical factors for UV protection efficacy.

In your case, adding 1% Glycerin and 1% Water Film (Galactoarabinan) to a sunscreen serum is considered a minor modification. Glycerin is a humectant and solvent, while Water Film (Galactoarabinan) is often used as a film-former and can potentially help improve the uniformity of the sunscreen film.

Given the low concentrations (1% each) and the nature of these ingredients (they are not primary UV filters), the impact on the SPF and PA values is expected to be minimal. As the staff reply indicated, minor adjustments with ingredients not directly related to SPF are unlikely to cause a significant change that would be a concern.

Therefore, while a slight theoretical change in SPF/PA is possible, adding 1% Glycerin and 1% Water Film (Galactoarabinan) is highly unlikely to cause a noticeable or significant alteration to the tested SPF and PA++ values of your sunscreen serum.