Ingredient Suitability and Formulation for Whitening and Moisturizing Soap Bars

Question

I am developing two soap bar formulas and would like expert advice on the ingredients. The first formula is for whitening, brightening, and aura, with the following ingredients:

[url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7/68-alpha-arbutin-%E0%B8%AD%E0%B8%B1%E0%B8%A5%E0%B8%9F%E0%B9%88%E0%B8%B2%E0%B8%AD%E0%B8%B2%E0%B8%A3%E0%B9%8C%E0%B8%9A%E0%B8%B9%E0%B8%95%E0%B8%B4%E0%B8%99-%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7%E0%B9%83%E0%B8%AA%E0%B8%AD%E0%B8%A2%E0%B9%88%E0%B8%B2%E0%B8%87%E0%B8%9B%E0%B8%A5%E0%B8%AD%E0%B8%94%E0%B8%A0%E0%B8%B1%E0%B8%A2.html:33jtadec]Alpha-Arbutin[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7/147-%E0%B8%81%E0%B8%A3%E0%B8%94%E0%B9%82%E0%B8%88%E0%B8%B4%E0%B8%81-kojic-acid-dipalmitate.html:33jtadec]Kojic Acid[/url:33jtadec]
isoflavone / [url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7/224-azelaic-acid-water-soluble.html:33jtadec]Azelaic Acid[/url:33jtadec] / [url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7/133-vitamin-c-l-ascorbic-acid-ultra-fine-%E0%B8%A7%E0%B8%B4%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B8%B4%E0%B8%99%E0%B8%8B%E0%B8%B5.html:33jtadec]L-ascorbic acid[/url:33jtadec] / [url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7/493-activated-resorcinol-4-butyl-resorcinol.html:33jtadec]resorcinol[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%82%E0%B8%B2%E0%B8%A7/133-vitamin-c-l-ascorbic-acid-ultra-fine-%E0%B8%A7%E0%B8%B4%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B8%B4%E0%B8%99%E0%B8%8B%E0%B8%B5.html:33jtadec]vit c[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/%E0%B8%95%E0%B9%89%E0%B8%B2%E0%B8%99%E0%B8%AD%E0%B8%99%E0%B8%B8%E0%B8%A1%E0%B8%B9%E0%B8%A5%E0%B8%AD%E0%B8%B4%E0%B8%AA%E0%B8%A3%E0%B8%B0/65-vitamin-e-tocopheryl-acetate-%E0%B8%A7%E0%B8%B4%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B8%B4%E0%B8%99%E0%B8%AD%E0%B8%B5.html:33jtadec]Vit E[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/%E0%B8%A1%E0%B8%AD%E0%B8%A2%E0%B8%8B%E0%B9%8C%E0%B9%80%E0%B8%88%E0%B8%AD%E0%B8%A3%E0%B9%8C/214-natural-moisturizing-amino-acids-%E0%B8%81%E0%B8%A3%E0%B8%94%E0%B8%AD%E0%B8%B0%E0%B8%A1%E0%B8%B4%E0%B9%82%E0%B8%99-%E0%B8%9A%E0%B8%B3%E0%B8%A3%E0%B8%B8%E0%B8%87%E0%B8%9C%E0%B8%B4%E0%B8%A7.html:33jtadec]Amino acid[/url:33jtadec] *เพิ่มฟอง

The second formula is for moisturizing, firming, and wrinkle reduction, with these ingredients:

หัวไชเท้า (Radish)
Cinnamon
[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%B8%8เชีย-%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%99%E0%B8%B4%E0%B8%8ค.html:33jtadec]shea butter[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/%E0%B8%A1%E0%B8%AD%E0%B8%A2%E0%B8%8ซ%E0%B9%8์%E0%B9%80%E0%B8%8จ%E0%B8%AD%E0%B8%A3%E0%B9%8์/1189-hyacoat-cationic-hyaluronic-acid.html:33jtadec]HyaCoat[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/whitening-%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B9%83%E0%B8%AB%E0%B9%89%E0%B8%9C%E0%B8%B4%E0%B8%A7%E0%B8%8ข%E0%B8%B2%E0%B8%A7/133-vitamin-c-l-ascorbic-acid-ultra-fine-%E0%B8%A7%E0%B8%B4%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B8%B4%E0%B8%99%E0%B8%8ซ%E0%B8%B5.html:33jtadec]vit c[/url:33jtadec]
[url=http://www.myskinrecipes.com/shop/%E0%B8%A1%E0%B8%AD%E0%B8%A2%E0%B8%8ซ%E0%B9%8์%E0%B9%80%E0%B8%8จ%E0%B8%AD%E0%B8%A3%E0%B9%8์/214-natural-moisturizing-amino-acids-%E0%B8%8ก%E0%B8%A3%E0%B8%94%E0%B8%AD%E0%B8%B0%E0%B8%ม%E0%B8%B4%E0%B9%82%E0%B8%99-%E0%B8%9A%E0%B8%B3%E0%B8%A3%E0%B8%B8%E0%B8%8ง%E0%B8%9C%E0%B8%B4%E0%B8%A7.html:33jtadec]Amino acid[/url:33jtadec] *เพิ่มฟอง

[url=http://www.myskinrecipes.com/shop/%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%AA%E0%B8%8ก%E0%B8%B1%E0%B8%94%E0%B8%98%E0%B8%A3%E0%B8%A3%E0%B8%A1%E0%B8%8ช%E0%B8%B2%E0%B8%95%E0%B8%B4/121-sweet-almond-oil-%E0%B8%99%E0%B9%89%E0%B8%B3%E0%B8%A1%E0%B8%B1%E0%B8%99%E0%B8%ส%E0%B8%A7%E0%B8%B5%E0%B8%97%E0%B8%AD%E0%B8%B1%E0%B8%A5%E0%B8%A1%E0%B8%AD%E0%B8%99%E0%B8%94%E0%B9%8์.html:33jtadec]Sweet Almond Oil[/url:33jtadec] scrub or [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%8ก%E0%B8%B1%E0%B8%94%E0%B8%98%E0%B8%A3%E0%B8%A3%E0%B8%A1%E0%B8%8ช%E0%B8%B2%E0%B8%95%E0%B8%B4/85-extra-virgin-olive-oil-%E0%B8%99%E0%B9%89%E0%B8%B3%E0%B8%A1%E0%B8%B1%E0%B8%99%E0%B8%ม%E0%B8%B0%E0%B8%8ก%E0%B8%AD%E0%B8%8ก-%E0%B8%9A%E0%B8%A3%E0%B8%B4%E0%B8%ส%E0%B8%B8%E0%B8%97%E0%B8%98%E0%B8%B4%E0%B9%8์.html:33jtadec]Olive Oil[/url:33jtadec] scrub

I have three questions regarding these ingredients for soap bar formulations:

Which ingredients from both formulas are not suitable for or less effective in wash-off products like soap?
What alternative ingredients should I use instead to improve the quality of the formulas?
Could you please recommend ingredients for both formulas?

MySkinRecipes Expert · Accepted Answer

Analysis and Recommendations for Soap Bar Formulations

Based on the ingredients provided for your two soap bar formulations and considering that soap is a wash-off product with a typically high pH, some ingredients are less stable or effective in this format.

Formula 1: White, Bright, Aura

Ingredients Not Suitable or Less Effective in Soap:

Alpha-Arbutin: This ingredient is sensitive to high pH and can break down in alkaline conditions like soap, reducing its effectiveness and potentially causing irritation. It is best used in leave-on products with a controlled pH.
L-ascorbic acid (Vitamin C): This form of Vitamin C is highly unstable in water and at the high pH of soap. It oxidizes quickly and loses its brightening and antioxidant properties in a wash-off product. It requires a low pH for stability and efficacy.
Isoflavone (Isoflaqua™): While water-soluble, the contact time in a wash-off product like soap is very short. The benefits for anti-aging and brightening are less likely to be significant compared to leave-on applications.
Natural Moisturizing Amino Acids: While beneficial for moisturizing, their effect in a wash-off product will be minimal as they are rinsed away. They might contribute to foam quality, but not significantly to skin moisturization in this format.
Activated Resorcinol™ (4-Butyl Resorcinol): Although it can be used up to 2% in wash-off products, its optimal pH for efficacy is lower, and it is light-sensitive. Maintaining its stability and effectiveness at the high pH of soap over time can be challenging.

Ingredients to Keep:

Kojic Acid Dipalmitate: While its optimal pH range is 3-9, it is more stable than Kojic Acid itself and can potentially offer some benefit, though efficacy might be reduced at very high soap pH.
Vitamin E (Tocopheryl Acetate): This is a stable antioxidant and skin conditioner that can be beneficial in soap.

Recommendations for Improvement (Replacements and Additions):

To enhance the whitening and brightening effects in a soap formula, consider ingredients that are more stable at higher pH or work through mechanisms suitable for wash-off:

Niacinamide (Vitamin B3): This is a stable whitening ingredient that works well in a broader pH range and offers multiple skin benefits, including improving skin barrier function. It is suitable for wash-off products.
Stable Vitamin C Derivatives: Instead of L-ascorbic acid, consider more stable derivatives like Sodium Ascorbyl Phosphate (SAP) or Magnesium Ascorbyl Phosphate (MAP). While their efficacy in wash-off is still debated compared to leave-on, they are much more stable in soap than L-ascorbic acid.

Formula 2: Moisturizing, Firming, Anti-wrinkle

Ingredients Not Suitable or Less Effective in Soap:

Radish: Without specific information on a cosmetic-grade radish extract, its stability and efficacy in soap are unknown. Many natural extracts degrade at high pH.
Cinnamon: Cinnamon can be a skin irritant, especially in wash-off products. Its benefits for firming or anti-wrinkle are not well-established in cosmetic science for a soap application.
L-ascorbic acid (Vitamin C): Same as in Formula 1, it is unstable in soap.
Natural Moisturizing Amino Acids: Similar to Formula 1, the moisturizing benefit in a wash-off product is limited.

Ingredients to Keep:

Shea Butter: An excellent emollient and moisturizer that is suitable for use in soap to help prevent dryness.
HyaCoat™ (Cationic Hyaluronic Acid): This is a highly suitable ingredient for moisturizing in wash-off products as it is designed to adhere to the skin even after rinsing.
Vitamin E (Tocopheryl Acetate): A stable antioxidant and skin conditioner beneficial in soap.
Sweet Almond Oil: A nourishing oil that contributes to the moisturizing properties of the soap.
Olive Oil: Another excellent emollient oil commonly used in soap making for its moisturizing benefits.

Recommendations for Improvement (Replacements and Additions):

To enhance the moisturizing and skin-conditioning properties, focus on ingredients known to work well in soap:

Glycerin: A humectant that draws moisture into the skin and is commonly used in soap to enhance hydration.
Optimize Oils and Butters: Ensure sufficient levels of nourishing oils and butters like Shea Butter, Sweet Almond Oil, and Olive Oil are used to provide a conditioning feel and combat the drying effect of soap.
HyaCoat™: Continue using HyaCoat™ for its unique ability to moisturize even after rinsing.

Using ingredients that are stable and effective within the constraints of a soap formulation will result in higher quality products that deliver the intended benefits more reliably.