Revised Vitamin C E Ferulic Serum Formula for Oily, Acne-Prone Skin

Thank you for sharing your revised formula and clarifying your goal of reducing irritation. Based on your original formula, the previous feedback, and the properties of the ingredients, here is a review and a suggested revised formula aiming for better compatibility and reduced irritation.

Your initial revised formula (100g):

• Water: 40g
• Triethanolamine (TEA): 2.5g
• Ferulic Acid: 1g
• Panthenol: 0.5g
• Ethoxydiglycol: 20g
• Propylene glycol: 10g
• Glycerin: 3g
• Laureth-23: 3g
• d-Alpha Tocopherol: 1g
• L-Ascorbic Acid: 12g
• Hyaluronic Acid Standard: 0.2g
• Hyaluronic Acid Nano: 0.8g
• Alpha Arbutin: 2g
• Niacinamide: 4g
• Phenoxyethanol: 1g
• Allantoin: 0.5g

Total: 101g

Feedback on Your Formula and Suggestions

1. Reducing Irritation: Your decision to reduce L-Ascorbic Acid to 12% is a good step. As discussed, removing Alpha Arbutin and Niacinamide is also recommended to simplify the formula and reduce potential irritation in this specific low-pH environment. Increasing Panthenol is beneficial for soothing.

2. Panthenol: You included 0.5g. Increasing Panthenol (Vitamin B5) to 3-5% is recommended for more effective soothing and irritation reduction, as mentioned in previous feedback. Let's aim for 3% in the revised formula.

3. Allantoin: You included 0.5g. While Allantoin is excellent for soothing, its solubility in water is limited to about 0.5% at room temperature and 0.2% if storing the final product in the refrigerator. Using 0.5g in a formula with only 40g water (1.25% of water) exceeds the solubility limit. Reducing it to 0.2g (0.2% of total formula) is appropriate and aligns with the previous feedback, ensuring it dissolves properly and provides soothing benefits within its solubility limits relative to the water content.

4. Ethoxydiglycol: You included 20g (20%). While Ethoxydiglycol (e.q. Transcutol) is a good solvent and carrier for ingredients like Ferulic Acid, the product description indicates a regulatory usage limit of not more than 2.6% for leave-on skin products. Using 20% is significantly above this recommended safety limit. It is crucial to adhere to recommended usage rates. We should drastically reduce this amount.

5. Hyaluronic Acid (Standard and Nano): You included 0.2g Standard and 0.8g Nano, totaling 1g (1%). The product descriptions recommend a total Hyaluronic Acid concentration (including Standard and Nano types) of 0.05-0.5% depending on skin dryness. While you reduced it to avoid a gel texture, 1% is still higher than the generally recommended range for hydration benefits and might still contribute to a thicker texture than desired for a serum. You can adjust this based on your preferred texture, but staying within or closer to the 0.5% total recommended maximum is advisable.

6. Laureth-23: This is a surfactant not typically needed in this type of serum. Removing it simplifies the formula.

7. Water Content: Removing Alpha Arbutin, Niacinamide, and Laureth-23 frees up space to increase the water content, which helps dissolve water-soluble ingredients and can make the serum feel less concentrated and potentially less irritating.

8. pH Level (Target 4.0): As discussed, pH 4.0 is acceptable for the efficacy of L-Ascorbic Acid, although a slightly lower pH (3.0-3.5) is often preferred for better long-term stability. Aiming for pH 4.0 is reasonable if you prioritize reduced irritation. You will need to add Triethanolamine (Triethanolamine 99%) gradually while measuring with a pH meter or strips to reach your target pH. Ensure the total amount of Triethanolamine does not exceed the recommended usage rate of 2.5%.

9. L-Glutathione from Capsule: As previously advised, L-glutathione from supplement capsules is unlikely to be pure and contains fillers. It's best to use cosmetic-grade ingredients. Also, it's generally recommended to formulate C E Ferulic and Glutathione formulas separately due to different optimal conditions.

10. Alpha Arbutin Formula: Since you removed Alpha Arbutin from this formula, you can use it in a separate whitening serum. Check the product page for Alpha Arbutin for recommended usage rates and formulation instructions. A simple water-based serum with humectants and a preservative is a common way to use it.

Suggested Revised Formula (Aiming for Less Irritation, 100g total)

Based on the feedback, here is a revised formula suggestion. Note that the water amount is approximate and should be adjusted at the end to reach a total of 100g after adding all other ingredients and adjusting pH.

• Water: ~65.6g (Adjust to 100g total)
• Triethanolamine (Triethanolamine 99%): Adjust pH to ~4.0 (Add drop by drop, measuring pH, ensure total TEA is <= 2.5g)
• Ferulic Acid (Pure-Ferulic Acid™): 1g
• Panthenol (Panthenol (Vitamin B5, DL-Panthenol, Powder)): 3g
• Ethoxydiglycol (Ethoxydiglycol (e.q. Transcutol)): 2.5g (Reduced to adhere to regulatory limit)
• Propylene glycol (Propylene Glycol): 10g
• Glycerin (Glycerin (USP/Food Grade)): 3g
• d-Alpha Tocopherol (Vitamin E (dl-alpha tocopherol)): 1g
• L-Ascorbic Acid (Vitamin C (L-ascorbic acid) (Ultra-Fine)): 12g
• Hyaluronic Acid Standard (Hyaluronic Acid (Standard Molecule)): 0.2g
• Hyaluronic Acid Nano (Hyaluronic Acid (Nano Molecule, 800daltons)): 0.3g (Reduced total HA to 0.5%)
• Phenoxyethanol (Phenoxyethanol (Extra Pure)): 1g
• Allantoin (Allantoin): 0.2g

Total (excluding TEA and final water adjustment): 1 + 3 + 2.5 + 10 + 3 + 1 + 12 + 0.2 + 0.3 + 1 + 0.2 = 36.2g
Water needed: 100g - 36.2g = 63.8g. (My initial estimate of 65.6g was close, use 63.8g and adjust slightly if needed after TEA).

Summary of Changes:

• Removed Alpha Arbutin, Niacinamide, and Laureth-23.
• Increased Panthenol to 3% for better soothing.
• Adjusted Allantoin to 0.2% of the total formula, which is within its solubility limit relative to the water content.
• Significantly reduced Ethoxydiglycol to 2.5% to comply with regulatory recommendations for leave-on products.
• Reduced total Hyaluronic Acid to 0.5% (0.2% Standard + 0.3% Nano) to be within the generally recommended usage range and potentially reduce gel texture.
• Increased Water content to balance the formula.

Important Considerations for DIY

• Hygiene: Maintain strict cleanliness during preparation.
• Accuracy: Use a precise scale for weighing ingredients.
• pH Adjustment: Use a pH meter or reliable strips to accurately adjust the pH with Triethanolamine. Add slowly.
• Stability: Store the serum in an airtight, opaque container in a cool, dark place (refrigeration is highly recommended for L-Ascorbic Acid serums). Observe for changes in color or odor.
• Patch Testing: Always test the final product on a small area of skin before facial application.

This revised formula addresses your goal of reducing irritation by adjusting key ingredients and concentrations based on product information and formulation principles. Remember that DIY formulations require careful execution and testing.