Lotion Formulation Review

Formula Assessment

Your proposed formula for a body lotion targeting keratosis pilaris and dry skin contains a good combination of exfoliating and moisturizing ingredients.

• Exfoliants (AHA/BHA): You are using 5% of Lactic Acid 90% Deodorized (equivalent to 4.5% active Lactic Acid) and 2% Salicylic Acid. The total active exfoliant concentration is 6.5%. While this blend of AHA and BHA can be effective for exfoliation and addressing clogged pores associated with keratosis pilaris, a combined concentration of 6.5% might be too strong and potentially irritating for dry and sensitive skin. It is recommended to start with lower concentrations (e.g., 2-3% Lactic Acid and 1% Salicylic Acid) and observe skin tolerance before increasing.
• Salicylic Acid Solubility: Dissolving 2% Salicylic Acid in only 5% Propylene Glycol is likely insufficient for complete dissolution. Salicylic Acid requires a higher ratio of solvent; Propylene Glycol can dissolve up to approximately 25% Salicylic Acid. To dissolve 2% Salicylic Acid, you would need at least 8% Propylene Glycol. Incomplete dissolution will result in a poor texture and reduced efficacy.
• Moisturizers and Skin Conditioners: Ingredients like Glycerin, Panthenol, Allantoin, Shea Butter, Sweet Almond Oil, and Safe B3 (Niacinamide) are excellent choices for providing moisture, soothing the skin, and supporting the skin barrier, which is important when using exfoliants.

Manufacturing Process Review

Your general process of creating separate water and oil phases, heating them, combining, and adding heat-sensitive ingredients later is appropriate for an emulsion.

• pH Adjustment (Step 6): This is the most critical step for AHA/BHA formulations.
  • Importance: AHA and BHA require a specific low pH (ideally 3.5-3.8) to be effective exfoliants and to ensure safety. If the pH is too high, they won't work. If it's too low, it can cause significant irritation.
  • Measurement: Litmus paper is not accurate enough for measuring the pH of cosmetic formulations, especially those with active ingredients like AHA/BHA. You must use a calibrated digital pH meter to get an accurate reading.
  • Adjustment: Since your formula contains acids, the initial pH will be low. You will likely need to raise the pH to the target range of 3.5-3.8. This is done by adding a dilute basic solution (like a 10% solution of Triethanolamine or Sodium Hydroxide) drop by drop to the cooled emulsion while blending, measuring the pH after each addition until the target pH is reached.

Cost Reduction Choices

Using standard Salicylic Acid and Lactic Acid 90% Deodorized are cost-effective options. Using Propylene Glycol as a solvent for BHA is also economical, provided you use enough to ensure the BHA is fully dissolved.

Additional Questions

• Squalane (Olive) during Pregnancy/Breastfeeding: Squalane (Olive) is generally considered safe and non-irritating, similar to the skin's natural sebum. While typically deemed safe for topical use during pregnancy and breastfeeding, it is always recommended to consult with a healthcare professional before using any new cosmetic products during this period.
• Vitamin E (Tocopheryl Acetate) for Rancidity: Vitamin E (Tocopheryl Acetate) is an antioxidant and can help protect oils from going rancid due to oxidation. However, the product description indicates it is less effective for this purpose compared to other forms of Vitamin E (like dl-alpha Tocopherol) or specialized antioxidants for oils. While 1% will provide some protection, it's a higher concentration than typically needed solely for preventing oil rancidity (0.01% is suggested for this purpose), and other antioxidants might be more efficient if rancidity is the primary concern.

Recommendations

1. Consider reducing the concentration of Lactic Acid and Salicylic Acid, especially if you have sensitive skin, and gradually increase if tolerated.
2. Increase the amount of Propylene Glycol to at least 8% to ensure the Salicylic Acid is fully dissolved.
3. Purchase a calibrated digital pH meter for accurate pH measurement.
4. Learn how to prepare and use a dilute basic solution (like Triethanolamine or Sodium Hydroxide) to adjust the pH of your final lotion to 3.5-3.8.