Formula Review: Stability, Preservation, and pH

Question

Please review the following cosmetic formula and provide feedback on its composition, stability, and compatibility:
6 g Arganoel (6 %)
4 g Jojobaoel (4 %)
3 g [url=http://www.myskinrecipes.com/shop/%E0%B8%99%E0%B9%89%E0%B8%B3%E0%B8%A1%E0%B8%B1%E0%B8%99%E0%B8%AA%E0%B8%81%E0%B8%B1%E0%B8%94%E0%B8%98%E0%B8%A3%E0%B8%A3%E0%B8%A1%E0%B8%8A%E0%B8%B2%E0%B8%95%E0%B8%B4/117-shea-butter-certified-organic-%E0%B9%80%E0%B8%8A%E0%B8%B5%E0%B8%A2-%E0%B8%9A%E0%B8%B1%E0%B8%95%E0%B9%80%E0%B8%95%E0%B8%AD%E0%B8%A3%E0%B9%8C-%E0%B8%AD%E0%B8%AD%E0%B8%A3%E0%B9%8C%E0%B9%81%E0%B8%81%E0%B8%B2%E0%B8%99%E0%B8%B4%E0%B8%84.html:2e3x8uxe]sheabutter[/url:2e3x8uxe] (3 %)
2 g [url=http://www.myskinrecipes.com/shop/emulsifier/141-light-cream-maker-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%AA%E0%B8%A3%E0%B9%89%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%99%E0%B8%B7%E0%B9%89%E0%B8%AD%E0%B8%84%E0%B8%A3%E0%B8%B5%E0%B8%A1.html:2e3x8uxe]Sodium Polyacrylate[/url:2e3x8uxe] (und) [url=https://www.myskinrecipes.com/shop/search?search_query=Polyisobutene+&orderby=position&orderway=desc:2e3x8uxe]Polyisobutene[/url:2e3x8uxe] (and) Water (2 %) 85 % Water (85 g) 1 g [url=https://www.myskinrecipes.com/shop/search?search_query=salicylic+acid&orderby=position&orderway=desc:2e3x8uxe]Salicylic Acid[/url:2e3x8uxe] (1 %)
1 g [url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B8%B2%E0%B8%AA%E0%B8%81%E0%B8%B1%E0%B8%94%E0%B8%9E%E0%B8%B7%E0%B8%8A%E0%B8%AA%E0%B8%A1%E0%B8%B8%E0%B8%99%E0%B9%84%E0%B8%9E%E0%B8%A3/69-licorice-extract-licochalcone-a-%E0%B8%8A%E0%B8%B0%E0%B9%80%E0%B8%AD%E0%B8%A1%E0%B9%80%E0%B8%97%E0%B8%A8-%E0%B8%AA%E0%B8%81%E0%B8%B1%E0%B8%94.html:2e3x8uxe]Licochalcone A[/url:2e3x8uxe] (1 %)
1 g [url=http://www.myskinrecipes.com/shop/%E0%B8%A3%E0%B8%B1%E0%B8%81%E0%B8%A9%E0%B8%B2%E0%B8%AA%E0%B8%B4%E0%B8%A7/252-zinc-pca-%E0%B8%8B%E0%B8%B4%E0%B8%87%E0%B8%84%E0%B9%8C-%E0%B8%9E%E0%B8%B5%E0%B8%8B%E0%B8%B5%E0%B9%80%E0%B8%AD.html:2e3x8uxe]Zinc PCA[/url:2e3x8uxe] (1 %)
3 g [url=http://www.myskinrecipes.com/shop/%E0%B8%A2%E0%B8%81%E0%B8%81%E0%B8%A3%E0%B8%B0%E0%B8%8A%E0%B8%B1%E0%B8%9A%E0%B8%9C%E0%B8%B4%E0%B8%A7/157-l-carnitine-%E0%B9%81%E0%B8%AD%E0%B8%A5%E0%B8%84%E0%B8%B2%E0%B8%A3%E0%B9%8C%E0%B8%99%E0%B8%B4%E0%B8%97%E0%B8%B5%E0%B8%99.html:2e3x8uxe]L-Carnitine[/url:2e3x8uxe] (3 %)
1 g [url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B9%88%E0%B8%A7%E0%B8%99%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%81%E0%B8%AD%E0%B8%9A%E0%B9%80%E0%B8%84%E0%B8%A3%E0%B8%B7%E0%B9%88%E0%B8%AD%E0%B8%87%E0%B8%AA%E0%B8%B3%E0%B8%AD%E0%B8%B2%E0%B8%87%E0%B8%84%E0%B9%8C/137-ethoxydiglycol-solvent-carrier.html:2e3x8uxe]Ethoxydiglycol[/url:2e3x8uxe] (1 %)
3 g [url=http://www.myskinrecipes.com/shop/%E0%B8%95%E0%B9%88%E0%B8%AD%E0%B8%95%E0%B9%89%E0%B8%B2%E0%B8%99%E0%B8%A3%E0%B8%B4%E0%B9%89%E0%B8%A7%E0%B8%A3%E0%B8%AD%E0%B8%A2/74-vitamin-b3-niacinamide-%E0%B8%A7%E0%B8%B4%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B8%B4%E0%B8%99%E0%B8%9A%E0%B8%B53.html:2e3x8uxe]Niacin[/url:2e3x8uxe]amid (3 %)
3 g [url=https://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B9%88%E0%B8%A7%E0%B8%99%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%81%E0%B8%AD%E0%B8%9A%E0%B9%80%E0%B8%84%E0%B8%A3%E0%B8%B7%E0%B9%88%E0%B8%AD%E0%B8%87%E0%B8%AA%E0%B8%B3%E0%B8%AD%E0%B8%B2%E0%B8%87%E0%B8%84%E0%B9%8C/143-glycerin-%E0%B8%81%E0%B8%A5%E0%B8%B5%E0%B9%80%E0%B8%8B%E0%B8%AD%E0%B8%A3%E0%B8%B5%E0%B8%99.html:2e3x8uxe]Glycerin[/url:2e3x8uxe] (3 %)
Hilfs- und Zusatzstoffe (1 g | 1 %):
1 g 1,3-[url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B9%88%E0%B8%A7%E0%B8%99%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%81%E0%B8%AD%E0%B8%9A%E0%B9%80%E0%B8%84%E0%B8%A3%E0%B8%B7%E0%B9%88%E0%B8%AD%E0%B8%87%E0%B8%AA%E0%B8%B3%E0%B8%AD%E0%B8%B2%E0%B8%87%E0%B8%84%E0%B9%8C/1337-1-3-propanediol.html:2e3x8uxe]Propanediol[/url:2e3x8uxe] [url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%81%E0%B8%B1%E0%B9%80%E0%B8%AA%E0%B8%B5%E0%B8%A2/642-ethylhexylglycerin-caprylyl-glycol.html:2e3x8uxe]Ethylhexylglycerin[/url:2e3x8uxe] (1 %)
71 g Water (71 %)

MySkinRecipes Expert · Accepted Answer

Feedback on Your Cosmetic Formula

Thank you for sharing your formula. It contains several beneficial ingredients for skin care.

Beneficial Ingredients: The formula includes nourishing oils like Argan Oil, Jojoba Oil, and Shea Butter, along with active ingredients such as Salicylic Acid, Licochalcone A, Zinc PCA, L-Carnitine, Niacinamide, and humectants like Glycerin and Ethoxydiglycol. These ingredients target various concerns like moisture, acne, inflammation, oil control, and skin renewal.

However, there are a couple of critical points to consider for the safety, stability, and efficacy of this formulation:

Preservation System: Your formula contains a high percentage of water, which is prone to microbial growth. While Ethylhexylglycerin is included, it is primarily a preservative booster and is not sufficient as a standalone broad-spectrum preservative. You must include a suitable broad-spectrum preservative system to prevent contamination and ensure the product's safety and shelf life.
pH Compatibility and Adjustment: This formula contains several active ingredients that function optimally at different pH ranges:
- Salicylic Acid is most effective at a low pH (acidic). Note that the powder form of Salicylic Acid is not water-soluble and needs to be dissolved in a suitable solvent like Ethoxydiglycol or Propanediol before adding to the water phase.
- Niacinamide is typically stable and effective in the pH range of 4.0-7.0.
- Licochalcone A works best between pH 3.5-6.5.
- Zinc PCA is most soluble in the pH range of 4-6 and stable between 3-7. It is also an electrolyte that can affect the viscosity of the Light Cream Maker™.
- L-Carnitine is stable between pH 3.5-8, with optimal skin compatibility and cell turnover effects often seen around pH 4-7.
  
  Achieving a single pH that is ideal for all these ingredients is challenging. You will need to carefully measure the final pH of your formulation and adjust it to a range that balances the efficacy and stability of your key actives while also being suitable for the skin (typically pH 4.5-5.5). You may need to use a pH adjuster (like Citric Acid or Sodium Hydroxide solution). Also, be mindful that Zinc PCA can interact with the Light Cream Maker™, potentially requiring adjustments to the cream maker concentration or specific mixing procedures as mentioned in the Light Cream Maker™ description.

In summary, while the selection of active ingredients is promising, adding a broad-spectrum preservative and carefully managing and adjusting the final pH are essential steps to create a safe, stable, and effective product.