A Guide To Common Skincare Ingredients

In cosmetic formulations, three fundamental component categories—water-based ingredients, oil-based ingredients, and surfactants—are directly related to product sensory performance. These components are also key determinants of a product’s texture and overall skin feel.

Although the variety of cosmetic products is extensive, certain representative ingredients are commonly found across formulations. A basic understanding of these ingredients can help consumers make more informed choices when selecting suitable products.

I. Water-Based Ingredients

Water-based ingredients refer to substances that are readily soluble in water but insoluble in oils.Their primary functions include maintaining skin hydration (moisturization), as well as imparting cooling or warming sensations to the product during application.

1. Glycerin (Glycerol / Concentrated Glycerin / Vegetable Glycerin)

Glycerin is a highly effective humectant with excellent long-term moisturizing capability. As it naturally exists in human skin, it exhibits very low irritation and sensitization potential. A notable characteristic is its exothermic reaction when mixed with water, which makes it suitable for use in warming-type cleansing products. Currently, plant-derived glycerin is the most widely used form.

2. 1,3-Butylene Glycol (1,3-Butanediol)

A commonly used humectant with low irritation potential, making it suitable for sensitive-skin formulations. It provides a light, non-sticky skin feel along with moderate moisturizing performance. Most commercially available 1,3-butylene glycol is synthetically produced, with limited plant-derived sources. It also exhibits mild antimicrobial properties and is often included in preservative-free formulations.

3. Ethanol (Alcohol)

Ethanol enhances product freshness and reduces greasiness. It is widely used as a solvent for ingredients with low water solubility. Due to its volatility, it provides a cooling sensation upon application. However, it may cause skin dryness and is generally not recommended for alcohol-sensitive or reactive skin types. Products formulated for sensitive skin are typically alcohol-free.

4. Dipropylene Glycol (DPG)

Dipropylene glycol has a moderately viscous yet non-greasy texture, delivering a smooth and refreshing skin feel. It helps improve skin softness and enhances product spreadability and glide. Additionally, it provides auxiliary preservative effects. However, high concentrations may cause mild irritation to the skin or eyes.

5. 1,3-Propanediol

A humectant with superior moisturizing performance compared to 1,3-butylene glycol and propylene glycol. It is commonly derived from the fermentation of corn sugar. Its use in cosmetic formulations has been increasing. While generally considered safe, comprehensive data on its effects on sensitive skin remain limited.

6. Sorbitol

Sorbitol is frequently used in both cosmetics and food products. It functions as a strong humectant similar to glycerin, retaining moisture by absorbing water. It is commonly found in toners and serums.

7. Sodium PCA (Sodium Pyrrolidone Carboxylate)

A natural moisturizing factor (NMF) present in the stratum corneum, Sodium PCA helps maintain skin hydration. As an amino acid derivative, it is highly effective even at low concentrations.

8. 1,2-Pentanediol

An effective humectant with additional preservative properties, commonly used in preservative-free formulations. It is typically synthetically produced, though plant-derived variants have emerged in recent years. It can also enhance water resistance in sunscreen formulations.

9. 1,2-Hexanediol

Similar in function to 1,2-pentanediol, but with stronger antimicrobial performance. However, it has relatively higher irritation potential, so it is generally used at low concentrations and less frequently in low-irritation formulations.

10. Propylene Glycol (PG)

Widely used in cosmetic formulations, often at relatively high concentrations. It has good moisturizing properties and enhances skin feel, but may cause irritation in some individuals.

Summary

It is important to distinguish between “safety” and “skin irritation” in cosmetics. Even products that are considered safe may still cause adverse skin reactions in certain individuals. Therefore, a patch test is recommended when trying new products.

II. Oil-Based Ingredients

Oil-based ingredients are substances that are soluble in oils within cosmetic formulations. Based on their origin, they can be classified into natural oils and synthetic oils. Natural oils include plant-derived, animal-derived, and mineral oils (mineral oils are often considered natural due to their origin).

From a chemical perspective, commonly used oil-based ingredients can be categorized into four main types:

1. Hydrocarbon Oils

Hydrocarbon oils exhibit high stability and effectively reduce transepidermal water loss. Due to their relatively large molecular size, they have limited penetration into the stratum corneum and primarily remain on the skin surface to provide a protective barrier. In cleansing oil formulations, they can significantly enhance cleansing efficiency.

Common examples: mineral oil, squalane (including plant-derived squalane), petrolatum, and liquid paraffin.

2. Ester Oils (Synthetic Oils) and Waxes

Ester oils possess properties intermediate between hydrocarbons and natural oils. They are highly stable and serve as effective emollients and skin protectants. There is a wide variety of ester oils. Waxes are natural substances primarily composed of ester compounds.

Common ester oils: ethylhexyl palmitate, triethylhexanoin, diisostearyl malate.

Common Waxes: jojoba oil, beeswax.