Serum Formulations for Combination Skin: Seborrheic Dermatitis & Anti-Aging

Hello! I understand you'd like help reviewing your cosmetic formulations, which you've adapted from recipes on our website and forum, to ensure they are suitable for your and your father's skin types, and you have questions about specific ingredients.

Based on your questions, the formulas provided, and the previous response from our staff, here is a summary and some additional recommendations:

Regarding the initial 5 formulas you previously inquired about:

1. Suitability for Oily/Combination Skin: As our staff previously informed you, Formulas 1 (Body Cream), 2 (Pitera Rose Hip Oil), and 3 (Ceramide Anti-Irritant Cream) contain oils (Rose Hip Oil) or ingredients that focus on high moisture (Galactomyces Ferment Filtrate, Ceramide Complex, Vitamin B5, Hyaluronic Acid Standard). These might be too heavy and feel greasy or uncomfortable for people with combination or oily skin. Formula 4 (Double Hyaluronic Acid) also contains Standard Hyaluronic Acid, which can feel sticky even at low concentrations for oily skin. The feel of Formula 5 (Hybrid Sunscreen) will primarily depend on the SPF Protect Ultra™ product itself, but sunscreens can generally feel heavier than regular moisturizers.

   Overall, based on the staff's feedback and the ingredients, most of the initial formulas seem more suited for normal to dry skin or specific concerns (irritation, dehydration) rather than being explicitly formulated for oily/combination skin to avoid greasiness/stickiness while providing moisture, anti-aging, and brightening.

2. Layering Formulas 2, 3, and 4: Layering these three specific formulas for combination/oily skin would likely feel too heavy and potentially redundant in terms of moisturizing benefits. Each formula already contains ingredients that might not be ideal for oily skin texture-wise. Combining ingredients from multiple formulas into one is possible in DIY formulation but requires careful consideration of solubility, compatibility, pH, and achieving the desired texture and feel, which is more complex than simply mixing. It would be better to select or adapt a formula specifically designed for oily/combination skin and add desired actives at appropriate concentrations, keeping the overall oil/heavy moisturizer content low, as suggested by our staff.

3. Usage Percentage for Rose Hip Oil: As our staff confirmed, natural oils like Rose Hip Oil can be used from 1-100%, meaning it can be applied directly to the skin. There is no strict maximum percentage for safety. However, when incorporating it into a cosmetic formula, the percentage used depends on the product type (serum, cream, lotion) and the desired skin feel. For combination/oily skin in a cream or lotion, a lower percentage than for dry skin is recommended to avoid a heavy or greasy feeling. The 5% used in your first and third formulas might still be high for oily skin.

Regarding the two new formulas you've asked about:

1. Review of New Formulas:

   • Formula 6 (for father, combination skin, seborrheic dermatitis): This formula contains several excellent ingredients for soothing irritation, reducing inflammation, and balancing the skin, making it suitable for combination skin with seborrheic dermatitis concerns. These include Beta Glucan, Calendula Extract, Allantoin, MSM, Zinc PCA, Licorice Extract, and Vitamin B3 (Niacinamide), which helps with oil balance and reducing inflammation.
     • Adjustments Recommended by Staff:
       • Allantoin Concentration: Staff noted that Allantoin is soluble in water up to 0.5% of the water content. In this formula (72.9% water), the maximum soluble amount is about 0.36%. Using 0.5% may result in undissolved Allantoin. Staff recommended reducing it to 0.2-0.3% (specifically 0.2% to avoid weighing errors with small amounts).
       • Hyaluronic Acid Nano: Staff recommended omitting this for your father's skin, as other ingredients provide sufficient moisture, and Hyaluron might feel sticky for some.
       • Licorice Extract: Staff recommended increasing the concentration to 1% for better efficacy against Sebderm.
     • Summary of Adjustments for Formula 6: Reduce Allantoin to 0.2-0.3%, remove Hyaluronic Acid Nano, increase Licorice Extract to 1%, and adjust the water percentage to reach 100% (water will increase from 72.90% to 73.30% or 73.20% depending on the Allantoin amount used).
   • Formula 7 (for user, combination skin, anti-aging, nourishing): This formula is well-focused on anti-aging and nourishing the skin. It includes Peptides (Argireline, Matrixyl 3000), Vitamin B3, and N-acetyl glucosamine for anti-aging and brightening, plus other extracts (Aloe Vera, Green Tea, Calendula, Licorice, Allantoin) for soothing and hydration.
     • Adjustments Recommended by Staff: Staff did not recommend specific adjustments for this formula but noted that the first new formula (Formula 6) is more focused on oil balance, making it generally more suitable for combination skin. However, this formula does contain Niacinamide, which helps with oil control, and uses Pro Polymer for texture, likely resulting in a light feel suitable for combination skin. The Allantoin concentration of 0.3% in 67.2% water is soluble (max ~0.336%).
     • Summary for Formula 7: This formula is good for its anti-aging and nourishing goals for combination skin. No major adjustments are necessary based on the ingredients and staff feedback.

2. Can Dry Skin Use the New Formulas? As staff mentioned, oil-balancing ingredients do not cause dryness. Both new formulas (especially Formula 7) contain several hydrating and soothing ingredients (e.g., Aloe Vera, Allantoin, Beta Glucan, Calendula, Licorice) and use Pro Polymer for a light, gel-like texture that provides hydration. Therefore, for people with slightly dry or dehydrated skin, these formulas could be suitable. They will not make the skin dry, but they may not provide as intense moisture as formulas specifically designed for very dry skin with higher oil or heavy humectant content. If used on slightly dry skin and it feels insufficient, a light additional moisturizer or oil can be applied afterwards.

I hope this information helps you in deciding and adjusting your formulas. If you have further questions or need more assistance with revisions, feel free to ask!