Cosmetic Formulation Q&A: Vitamin C, pH, Ingredients, and Delivery

Asked by: tou_lusifel On: January 25, 2013 Product Type: Cosmetics

Question

I have several questions about cosmetic formulations based on previous topics:

  1. Regarding the Anhydrous Vit C formula mentioned previously, how does its efficacy compare to Ethyl ascorbic acid after mixing?
  2. What is the typical texture of an anhydrous Vit C formula after mixing (e.g., cream, gel, oil)? How is its absorption?
  3. After mixing, will an anhydrous Vit C formula have an acidic pH, given that L-ascorbic is an acid?
  4. If I apply an acidic substance like Vit C and then immediately apply a cream with a neutral pH, will this affect both substances?
    • Will the Vit C become less effective because the neutral cream makes the environment relatively more alkaline?
    • Will the neutral cream also be less effective due to the acidity of the Vit C?

      Is my understanding correct?
  5. In cases where certain ingredients work best in an acidic environment, but we need to add a base to adjust the final pH to be compatible with human skin, does this pH adjustment reduce the efficacy of the active ingredient? For example, if an ingredient works best in an acidic state but we add a base to make the overall pH skin-compatible, does adding the base make that ingredient less effective?
  6. Are Allantoin, bisabolol, and betaine all used for anti-irritation? Which one is the most effective?
  7. Is the purpose of liposomes, commonly used in cosmetics, to deliver active ingredients into skin cells? How can we know which specific active ingredients will be delivered into the skin cells, especially if the formula contains many different active ingredients?
  8. What are the differences in usage between Propylene glycol and Butylene glycol?

Thank you.

Answer

Answers to your questions about cosmetic formulations:

  1. Anhydrous Vit C (L-Ascorbic Acid) vs. Ethyl Ascorbic Acid (EAA) efficacy:

    • L-Ascorbic Acid (L-AA) is the pure form and potentially the most potent if stable and delivered effectively. Anhydrous formulas aim for stability.
    • Ethyl Ascorbic Acid (EAA) is a stable derivative that penetrates well and converts to L-AA in the skin.
    • Both can be highly effective; efficacy depends heavily on the specific formulation, concentration, stability, and penetration. A well-formulated anhydrous L-AA can be very potent, as can a stable EAA serum.

  2. Anhydrous Vit C texture and absorption:

    • Anhydrous means without water. The texture is typically oily, balm-like, or a thick serum using bases like silicones, oils, or glycols.
    • Absorption varies depending on the base ingredients and penetration enhancers used in the formulation.

  3. Anhydrous Vit C pH after mixing/application:

    • Yes, L-Ascorbic Acid is an acid. While the anhydrous formula has no pH, upon contact with skin moisture or water-based products, the L-AA dissolves and creates an acidic environment (ideally pH 2.5-3.5 for optimal penetration).

  4. Layering acidic Vit C and neutral cream:

    • Correct. Layering an acidic product with a higher pH product will cause mixing on the skin surface.
    • This raises the pH of the Vit C layer, potentially reducing L-AA penetration and efficacy.
    • It also lowers the pH of the subsequent cream, potentially affecting the stability or efficacy of its pH-sensitive ingredients.

  5. Adjusting pH of active ingredients:

    • Correct. If an active ingredient works best at a specific pH (e.g., acidic) but the final product's pH is adjusted away from this optimum (e.g., raised for skin comfort), it can reduce the efficacy of that active ingredient. Formulators balance optimal active pH with skin compatibility pH.

  6. Allantoin, Bisabolol, Betaine for soothing/anti-irritation:

    • Yes, all three are used for soothing, hydrating, or anti-irritant properties.
    • Allantoin: Soothing, healing, moisturizing.
    • Bisabolol: Strong anti-inflammatory, redness reduction.
    • Betaine: Humectant, osmoprotectant, reduces irritation from surfactants, improves hydration.
    • There is no single "best"; they have slightly different mechanisms and are often used together for synergistic effects. Bisabolol is often noted for potent anti-inflammatory action.

  7. Liposomes as delivery systems:

    • Yes, liposomes encapsulate actives to enhance skin penetration.
    • They encapsulate actives based on solubility: water-soluble in the core, lipid-soluble in the membrane. They don't selectively "know" which active to deliver based on function, but rather encapsulate compatible actives present during formation.
    • Encapsulated actives are delivered together when liposomes interact with skin cells.

  8. Propylene Glycol vs. Butylene Glycol usage:

    • Both are humectants, solvents, and penetration enhancers.
    • Propylene Glycol: Very common, effective solvent. Historically associated with potential irritation at high levels, though generally safe.
    • Butylene Glycol: Often perceived as slightly milder, can provide a different skin feel (less sticky). Also a good solvent and humectant.
    • Formulators choose based on solubility needs, desired texture, cost, and target audience (BG sometimes preferred for sensitive skin).

Tags

Cosmetic Formulation Ingredient Comparison Ingredient Interaction Liposome pH Adjustment