Adjusting Cream Texture, Vitamin C/B3 Compatibility, and Sunscreen for Actives

Here are the answers to your questions regarding your whitening cream formulation:

1. Texture Issue: The thinning after adding Soy Extract is likely because it's water-based. To thicken your lotion-like texture to a creamier consistency without stickiness, gradually add Pro Polymer (ID: 234) in 0.5% increments while mixing until fully dissolved. This was recommended by the staff and should provide a thick yet light feel in a formula with oils and emulsifiers.
2. Adding Glycolic Acid: Glycolic Acid (ID: 660) can help with melasma but will thin the formula. You can add around 3% by reducing the water content accordingly. You will need to use a thickener like Pro Polymer to achieve the desired consistency after adding Glycolic Acid.
3. Vitamin C and B3 Interaction: Yes, Vitamin C (including common derivatives) and Niacinamide (B3) can interact, reducing efficacy and potentially causing irritation. This applies generally, and there are no common derivatives that are exceptions when mixed directly.
4. Vitamin C and B3 Usage Timing: Using a Vitamin C serum and a B3 cream at different times of the day (e.g., morning and night) is a practical approach. Ingredients are absorbed over time, so applying them separately allows each to work effectively. You don't need to avoid B3 creams entirely if you use a Vitamin C serum, just avoid layering them immediately.
5. Masking Base Cream Smell: There's no specific ingredient to eliminate the base smell. The key is selecting a fragrance with a profile strong enough to mask or blend well with the chemical odors.
6. Sun-Sensitive Actives and Sunscreen: Sunscreen protects your skin from UV, which is vital. While UV can degrade actives, they are absorbed into the skin over time. Sunscreen helps protect the skin surface, but the active's efficacy relies more on its absorption. Add sunscreen for skin protection at the appropriate concentration for the desired SPF.