Skin Absorption of Water-Soluble Ingredients

Regarding your question about whether water-soluble ingredients like Alpha Arbutin, Vitamin B3 (Niacinamide), N-Acetylglucosamine, and Vitamin B5 (Panthenol) require a carrier such as Ethoxydiglycol for skin absorption:

Generally, water-soluble active ingredients can be absorbed by the skin even without a specific carrier. The skin's absorption process is complex and influenced by many factors beyond just the presence of a carrier.

While not strictly necessary for absorption, ingredients like glycols (including Ethoxydiglycol) are frequently used in formulations for other important reasons:

• Improving Skin Feel: Glycols can enhance the texture and feel of a product on the skin, making it more pleasant to apply and encouraging proper spreading and contact time, which indirectly helps the active ingredients work.
• Acting as Solvents: Some active ingredients, even if generally considered water-soluble, may require a co-solvent like a glycol to fully dissolve or remain stable in a complex formulation.

For ingredients like Vitamin C (L-Ascorbic Acid), while it is water-soluble, its stability in water can be an issue depending on the form and the formula's pH. Other stable water-soluble Vitamin C derivatives like Ascorbyl Glucoside or Ethyl Ascorbic Acid are also available. The overall formulation, including pH and other ingredients, plays a significant role in the effectiveness and absorption of Vitamin C, rather than solely relying on a carrier.

In summary, while carriers like Ethoxydiglycol can serve multiple beneficial roles in a cosmetic formulation, they are not always essential for the skin absorption of inherently water-soluble active ingredients. The decision to include them often relates more to optimizing the product's texture, stability, and the solubility of various components within the formula.