PEG-100 Stearate acts as a highly effective, non-ionic emulsifier that facilitates the blending of oil and Aqua to create stable, cosmetically elegant lotions. By significantly increasing the HLB (Hydrophilic-Lipophilic Balance) of a formulation, it ensures that products remain uniform and resist phase separation under various temperatures.
- INCI Name:
- PEG-100 Stearate
- Chemical/Scientific Name:
- Polyethylene Glycol (100) Monostearate
- Common Aliases:
- Polyoxyethylene (100) Stearate, POE (100) Monostearate
| Category: | Emulsifiers, Surface-Active Substances |
| Source Origin: | Synthetic (Derived from Stearic Acid and ethylene oxide) |
| Comedogenic Rating: | 0–1 |
| Primary Industries: | Cosmetics, Dermatology, Pharmaceuticals |
| Solubility: | Water-soluble |
At a Glance: Properties & Effects
| Formula Stability: | |
| Texture Enhancement: | |
| Irritation Risk: | |
| Penetration Enhancement: |
Primary Benefits:
- Prevents oil and water components from separating in creams.
- Creates a lightweight, non-greasy skin feel compared to other heavy waxes.
- Supports the uniform distribution of active ingredients across the skin surface.
- Enhances the washability of oil-based cleansers and balms.
Potential Risks:
- May cause mild irritation on extremely compromised or broken skin barriers.
- Historical concerns regarding trace impurities like 1,4-dioxane, though modern cosmetic grade standards strictly control these levels.
Biological Action & Cosmetic Profile
As a polyethylene glycol ester of Stearic Acid, this ingredient functions primarily as a non-ionic surfactant. Its molecular structure contains a long lipophilic tail (the stearate) and a large hydrophilic head (the 100 units of ethylene oxide). This configuration gives it an exceptionally high Hydrophilic-Lipophilic Balance (HLB) value of approximately 18.8, making it an ideal candidate for oil-in-water (O/W) emulsions where a high degree of water solubility is required.The molecule works by reducing the interfacial tension between immiscible liquids. In a typical skincare formulation, it surrounds oil droplets, positioning its fatty acid chains inward toward the oil and its polyethylene glycol chains outward toward the water phase. This orientation creates a protective barrier around the oil droplets, preventing them from coalescing and causing the product to break or “split.”Formulators frequently employ this material to achieve specific rheological properties. Unlike many traditional emulsifying waxes that can feel heavy or tacky, this ester provides a “slip” that facilitates even spreading. Because it is non-ionic, it maintains stability in the presence of electrolytes, making it compatible with various botanical extracts and minerals that might destabilize ionic emulsifiers.
Broader Applications & Origins
While predominantly used in leave-on moisturizers, the ingredient serves a critical role in rinse-off systems. In cleansing balms, it acts as the primary mechanism for “rinsing clean,” allowing the oils in the balm to emulsify with water and wash away without leaving a film. Beyond the personal care industry, similar PEG-esters are utilized in the pharmaceutical sector to stabilize topical medications and improve the consistency of medicated ointments.Production involves the ethoxylation of Stearic Acid. While Stearic Acid can be derived from animal fats or vegetable oils (like palm or coconut), the cosmetic industry overwhelmingly utilizes plant-derived sources for this synthesis. The “100” in the name refers to the average number of ethylene oxide monomer units attached to the fatty acid chain, which dictates the ingredient’s high solubility and specific functional profile.
Routine Integration
Synergies:
- Glyceryl Stearate: This is the most common pairing; together, they form a “self-emulsifying” base that creates extremely stable emulsions.
- Fatty Alcohols: Ingredients like Cetearyl Alcohol or cetyl alcohol help build viscosity and body in formulas using this emulsifier.
- Humectants: Works seamlessly with Glycerin and Sodium Hyaluronate to maintain hydration within the emulsion structure.
Conflicts:
- No known direct chemical conflicts with active ingredients like Retinol or Ascorbic Acid.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel has repeatedly evaluated PEG-100 Stearate and concluded it is safe for use in cosmetic formulations. Clinical studies indicate that it is neither a significant skin irritant nor a sensitizer, even at high concentrations. Although the manufacturing process involves ethylene oxide—which can produce 1,4-dioxane as a byproduct—modern cosmetic manufacturing utilizes vacuum stripping and purification techniques to ensure these impurities are either non-detectable or significantly below the safety thresholds established by the SCCS and FDA. Furthermore, due to its high molecular weight, the ingredient does not readily penetrate through intact human skin, remaining on the surface or within the stratum corneum.
Is PEG-100 Stearate safe for acne-prone skin?
Yes. It has a very low comedogenic rating (0–1), meaning it is unlikely to clog pores or exacerbate acne. It is often chosen for “oil-free” or “non-comedogenic” formulations because it provides a lightweight finish without the heaviness of natural waxes.
Is this ingredient natural or synthetic?
It is a synthetic ingredient. While the fatty acid component (Stearic Acid) is often derived from natural plant oils, the ethoxylation process that creates the PEG portion is a chemical synthesis.
Does PEG-100 Stearate cause skin irritation?
For the vast majority of users, it is non-irritating. However, people with extremely sensitive skin or a compromised skin barrier (such as active eczema) should patch-test products containing PEGs, as they can occasionally facilitate the penetration of other potential irritants.