Advice for Glycerin Bar Soap for Sensitive, Acne-Prone Skin

Thank you for your question regarding the glycerin bar soap you made. We understand you are looking for ways to improve foaming, preservation, fragrance longevity, and general suitability for sensitive, acne-prone skin.

As previously mentioned by our staff, it is important to note that traditional bar soaps, including glycerin melt-and-pour bases, typically have a high pH (alkaline). Healthy facial skin has a slightly acidic pH (around 5-6). Using a high-pH cleanser can disrupt the skin's natural barrier, potentially leading to dryness, irritation, and worsening of conditions like sensitivity and acne. For sensitive, acne-prone facial skin, we generally recommend using low-pH liquid cleansers or syndet bars which are formulated to be closer to the skin's natural pH.

However, if you wish to modify your current glycerin bar soap base, here is some information based on your questions:

1. Foaming Agent

To increase foam in your soap base, you can add gentle, mild surfactants. Some options that are suitable for cleansing products and known for good foam are:

• Creamy Foamer™ (Sodium Methyl Cocoyl Taurate): This is a gentle anionic surfactant that creates soft, smooth foam. It is recommended for use in skin cleansing products at a rate of 3-30% (recommended 10-15%). It dissolves in water and can be gently heated (below 50°C) if needed. It produces the most foam around pH 6.3.
• BabyFoam™ (Sodium Cocoyl Isethionate): A very gentle anionic surfactant in fine powder form, suitable for creamy or solid formulas like syndet bars or cleansing powders. It provides high foam. Usage rate is 5-60%. It dissolves in water and can withstand heat.
• IseFoam™ (Sodium Lauroyl Methyl Isethionate): Another gentle anionic detergent that produces good foam. Usage rate is 1-15%. It dissolves in water.

When adding surfactants to a melt-and-pour base, ensure they are fully incorporated by melting the base gently and stirring carefully to avoid excessive bubbles during mixing.

2. Preservatives

Adding water-based ingredients or botanical extracts to your soap increases the risk of microbial growth. While bar soaps are less prone to contamination than liquid products due to their low water activity when dry, adding external ingredients necessitates considering preservation, especially if the soap might be exposed to moisture during use or storage.

Some broad-spectrum preservatives that could be considered, keeping in mind the pH limitations of a bar soap base:

• NaturePreserve™ Ultra (Gluconolactone & Sodium Benzoate): A natural preservative effective in the pH range of 3-6. Usage rate 0.75-2.0% (recommended 1.25%). It's a powder and dissolves in water.
• Global Guard™ 221 (Dehydroacetic Acid & Benzyl Alcohol & Water): A broad-spectrum preservative effective at pH 2-7. Usage rate 0.5-1.1%. It's a liquid and should be added below 45°C.
• Mild Preserved™ COS (Phenoxyethanol & Chlorphenesin & Caprylyl Glycol): A broad-spectrum preservative effective at pH 2-8. Usage rate 0.75-1.5%. It's a liquid and should be added below 45°C.
• Preserve-BSB™ (Benzyl Alcohol & Sodium Benzoate & Potassium Sorbate & Aqua): Effective up to pH 5.5. Usage rate 0.3-1.0%. Dissolves in the water portion.
• NaturePreserve™ LB2 (Dehydroacetic Acid & Benzoic Acid & Benzyl Alcohol & Water): Effective at pH 2.0-6.5. Usage rate 0.5-1.0%. Dissolves in the water portion, avoid heat above 50°C.
• Zinc Chloride: Can act as an anti-microbial agent effective against P.Acnes and also has astringent properties. Usage rate 0.1-1.0%. Soluble in water.

It is crucial to check the pH of your final soap product after adding ingredients and select a preservative that is effective within that pH range. A challenge test is always recommended to confirm the efficacy of the preservative in your specific formula.

3. Fragrance Longevity

Retaining the scent of essential oils or fragrances in a high-pH bar soap can be challenging as the alkaline environment can degrade some fragrance components. There are no simple ingredients to add to a melt-and-pour base that act as strong fragrance fixatives in this environment. Some ingredients might act as carriers, but significant fragrance fade is common in traditional bar soaps over time.

4. Suitable Additives for Sensitive, Acne-Prone Skin

To make the soap more suitable for sensitive, acne-prone skin (while still acknowledging the pH limitation), you can add ingredients known for soothing, anti-inflammatory, or anti-acne properties:

• Licorice Extract (Licochalcone A): Helps reduce skin inflammation, redness from acne, irritation, and oiliness. Usage rate 0.5-3% (recommended 0.5-1.0% for acne/oiliness). Mix in the water phase, pH 3.5-6.5.
• Pep®-Acne (Oligopeptide-10): An anti-microbial peptide effective against acne-causing bacteria. Usage rate 5%. Soluble in water, avoid heat.
• Pep-Calm™ (Palmitoyl Tripeptide-8): Effective in reducing skin redness and irritation. Usage rate 1.0-2.5%. Mix in water, avoid heat, pH 5.2-7.2.
• Portulaca Extract: Known for reducing skin irritation. Usage rate 0.1-0.5%. Mix in water, avoid heat.

When adding these ingredients, ensure they are compatible with the soap base and add them at appropriate temperatures (usually when the melted base has cooled slightly but is still liquid) to avoid degrading heat-sensitive components.

In summary, while you can modify your glycerin bar soap base with foaming agents, preservatives, and beneficial extracts, the inherent high pH of traditional bar soap remains a significant factor for sensitive, acne-prone facial skin. Considering a low-pH liquid cleanser or syndet bar formulation might be a more effective long-term solution for these skin concerns.