Formula Review for Treatment Lotion (น้ำตบ)

Your proposed formula for the Treatment Lotion (น้ำตบ) looks quite interesting. It contains several good ingredients focused on skin soothing (Chamomile, Calendula), hydration (Wakame, Palmaria, WaterSoft, Water lock), and includes Niacinamide which helps with the skin barrier, reducing inflammation, and improving skin tone.

The percentages of most ingredients seem appropriate for use in a watery product like a treatment lotion, with Chamomile Water as the main base and extracts/actives at levels expected to show benefits.

However, there are some crucial components necessary for water-based formulas that are currently missing. You should consider adding these to make the formula complete, safe, and stable.

Additional Recommendations:

1. Preservative: Water-based formulas absolutely require a preservative system to prevent the growth of microorganisms (bacteria, mold, yeast) which can spoil the product or be harmful to the skin. The absence of a preservative is the most significant risk for this formula. It is essential to add a suitable preservative for water-based products with a neutral to slightly acidic pH, used at the manufacturer's recommended rate. Adding a preservative will require slightly reducing the percentage of Chamomile Water to keep the total at 100%.
2. pH Adjustment: The pH of the final product should be within a range suitable for the skin (generally 4.5-6.5) for the efficacy of certain ingredients (e.g., Niacinamide works well between pH 5-6) and to avoid skin irritation. After mixing all ingredients, you should measure the pH and adjust it if necessary using a mild acid (like Lactic Acid or Citric Acid solution) or a mild base (like Sodium Hydroxide solution).
3. Chelating Agent: Adding a small amount of a chelating agent (e.g., Disodium EDTA or Tetrasodium EDTA at around 0.05-0.2%) helps to sequester metal ions that might be present in the water or extracts. This can improve the efficacy of the preservative and prevent formula degradation.
4. Basic Humectant (e.g., Glycerin or Propanediol): Although you have WaterSoft and Water lock, adding a small amount (e.g., 2-5%) of Glycerin or Propanediol can enhance the humectant effect and improve the texture of the product.

Summary:

Your initial formula has good and interesting ingredients, but the most important thing to add is a "preservative" for the safety and shelf life of the product. You should also check and adjust the pH to be within a skin-compatible range. Additionally, considering a chelating agent and a basic humectant are good options for further improving the formula.

Once you adjust the formula, you should test the compatibility of the ingredients, the stability of the product (e.g., color, odor, clarity), and test for skin irritation.

I hope this advice is helpful!