2-Hexanediol is a humectant and preservative booster commonly used in skincare products to help retain moisture and extend shelf life. It works by drawing water into the skin while also enhancing the effectiveness of other preservatives, allowing brands to use lower amounts of traditional preservatives.
Benefits
Hydrates and moisturizes skin by drawing in water
Helps preserve products with lower preservative levels
Works synergistically with other skincare ingredients like niacinamide
Potential concerns
May cause cell viability concerns at concentrations above 1.0% in laboratory studies
Limited real-world safety data in humans at typical skincare concentrations (usually 2-5%)
Potential environmental concern if released into water systems
Science: While 2-hexanediol is widely used as a preservative substitute for parabens, recent cytotoxicity studies raise questions about safety at concentrations commonly found in skincare products (>2%). However, these findings are from laboratory cell studies and may not directly translate to human skin application. Further human safety studies are needed to confirm real-world risk.
Glycerin is a naturally-derived humectant—a substance that draws water into the skin from the air and deeper skin layers. It's a common moisturizing ingredient used across skincare products to improve hydration and skin softness.
Benefits
Increases skin hydration by attracting moisture to the outer layers
Helps maintain skin barrier function and protects against dryness
Generally well-tolerated and suitable for most skin types, including sensitive skin
Science: A comprehensive safety assessment by the Cosmetic Ingredient Review Expert Panel concluded that glycerin is safe as used in cosmetics. Research supports its role as a humectant and skin conditioning agent, and it has been studied as part of broader skincare treatments for conditions like seborrheic dermatitis.
Caprylyl glycol is a humectant and preservative booster derived from coconut oil. It helps products stay fresh by inhibiting microbial growth, while also drawing moisture into the skin.
Benefits
Helps preserve products and reduce need for traditional preservatives
Hydrates skin by attracting and retaining moisture
Lightweight texture that absorbs easily
Potential concerns
Rare but documented cases of allergic contact dermatitis in sensitive individuals
May cause irritation in very sensitive or compromised skin at high concentrations
Science: A 200-subject patch test found no delayed hypersensitivity reactions to caprylyl glycol in preservative mixtures. However, isolated case reports have identified it as a contact allergen in susceptible individuals. Recent market analysis confirms it is used at safe, regulated levels in cosmetic formulations.
Propanediol is a lightweight humectant and solvent derived from natural sources like glycerin. It helps skin retain moisture and improves the texture and spreadability of skincare formulations.
Benefits
Hydrates and plumps the skin
Improves product texture and absorption
Lightweight alternative to glycerin
Science: Propanediol can be produced through environmentally friendly fermentation processes using microorganisms, making it a sustainable alternative to chemically synthesized versions. It is widely recognized as safe in cosmetic applications and is commonly used in skincare products as both a humectant and preservative booster.
Caprylic/Capric Triglyceride is a lightweight oil derived from coconut that acts as an emollient and carrier ingredient in skincare products. It helps soften the skin, improve product texture, and allows other active ingredients to penetrate more effectively.
Benefits
Improves skin hydration and reduces water loss from the skin
Creates a smooth, non-greasy feel on the skin
Helps deliver other active ingredients deeper into the skin
Supports the skin's natural moisture barrier
Science: Research shows that products containing 15% caprylic/capric triglyceride increase skin hydration and reduce transepidermal water loss (TEWL), likely through an occlusive moisturizing effect. The ingredient is also commonly used as an effective carrier oil in cosmetic formulations to enhance penetration of other skincare actives.
Pentylene glycol is a humectant—a moisture-binding ingredient that helps skin retain water and feel hydrated. It's commonly used in skincare formulations to improve texture and maintain product stability.
Benefits
Draws moisture into the skin for improved hydration
Helps products feel smoother and lighter on the skin
Contributes to product preservation and stability
Potential concerns
May cause contact allergic reactions in sensitive individuals—classified as an emerging cosmetic allergen
Rare cases of contact dermatitis have been reported
Science: Safety studies show pentylene glycol has a high margin of safety in typical skincare use, with low skin penetration due to its volatility. However, recent dermatological literature identifies it as an emerging allergen capable of causing contact sensitivity in some individuals, so patch testing is recommended for those with sensitive or reactive skin.
Citric acid is a naturally occurring organic acid commonly used in skincare products as an exfoliating agent and pH balancer. It belongs to a group of acids called alpha-hydroxy acids (AHAs) that work by gently removing dead skin cells from the surface to improve skin texture and appearance.
Benefits
Gentle chemical exfoliation to remove dead skin cells
Helps improve skin texture and reduce appearance of keratoses
Can help with acne-prone skin when used appropriately
Balances product pH
Potential concerns
May cause irritation, redness, or sensitivity, especially with frequent use or in sensitive skin
Can increase sun sensitivity — sunscreen use is recommended when using AHA products
Higher concentrations may cause stinging or dryness
Science: Citric acid is a well-established AHA used in cosmetic formulations for superficial skin peeling. Research indicates AHAs including citric acid have dual effects on skin and warrant caution regarding adverse reactions, particularly with concentration and frequency of use.
Sodium hydroxide is a strong alkaline ingredient used in skincare primarily as a pH buffer to neutralize acids and adjust the acidity level of formulations. It is not typically used as an active skincare ingredient but rather as a processing aid to achieve the correct pH balance for product stability and skin compatibility.
Benefits
Neutralizes acidic ingredients to create balanced pH formulations
Helps stabilize skincare products
Enables use of potent acid-based actives by buffering them to safer pH levels
Potential concerns
Can cause severe burns and irritation if used in high concentrations or improperly formulated
Highly alkaline products may disrupt skin's natural acid mantle and cause irritation, dryness, or sensitivity
Risk of harm increases significantly if products are not properly pH-balanced by manufacturers
Science: The research provided focuses on sodium hydroxide as a medical cauterant for surgical procedures at 10% concentration, which is not relevant to cosmetic skincare use. In properly formulated consumer skincare products, sodium hydroxide is used in trace amounts solely for pH adjustment and poses minimal risk when the final product pH is within safe ranges (typically 4.5-7.0 for facial products).
