Polyethylene Glycol 400 (PEG-400) is a versatile, water-soluble liquid that functions as a highly effective humectant, solvent, and penetration enhancer. It improves the spreadability of skincare products while ensuring that active ingredients are delivered efficiently into the skin.
- INCI Name:
- PEG-8
- Chemical/Scientific Name:
- Polyethylene Glycol 400; Polyoxyethylene (8) Glycol
- Common Aliases:
- Macrogol 400, PEG-400
| Category: | Solvents |
| Source Origin: | Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Cosmetics, Pharmaceuticals, Food |
| Solubility: | Water, Alcohol Denat., Glycols |
At a Glance: Properties & Effects
| Hydration/Moisture: | |
| Penetration Enhancement: | |
| Formula Stability: | |
| Irritation Risk: |
- Primary Benefits: Attracts and retains moisture, stabilizes complex emulsions, increases the efficacy of other active ingredients by facilitating skin entry.
- Potential Risks: Generally non-irritating, though high concentrations may cause mild warmth or stinging on compromised skin barriers.
Biological Action & Cosmetic Profile
Polyethylene Glycol 400 operates as a polymer of ethylene oxide with a clear, viscous consistency. Its numerical designation (400) refers to its average molecular weight, which translates to approximately 8 to 9 ethylene oxide units, hence the INCI name PEG-8. This specific molecular weight allows it to remain in a liquid state at room temperature, making it an ideal vehicle for dissolving various cosmetic actives that are otherwise difficult to incorporate into Aqua-based solutions.The primary mechanism of PEG-400 involves high hygroscopicity. Similar to Glycerin, it forms hydrogen bonds with water molecules, effectively “trapping” hydration within the skin’s upper layers. Beyond simple hydration, it functions as a potent penetration enhancer. By temporarily modifying the permeability of the stratum corneum, it assists larger or polar molecules in bypassing the skin’s lipophilic barrier, thereby increasing the bioavailability of the formulation.Structural stability is another hallmark of this ingredient. It is chemically inert, meaning it does not readily react with other components in a formula, which helps preserve the shelf life of products containing sensitive actives. In many serum formulations, it provides a “slip” that improves the consumer experience during application, reducing friction and ensuring an even distribution of the product across the face.
Broader Applications & Origins
While extensively used in personal care, PEG-400 is a staple in the pharmaceutical industry as an excipient for oral and topical medications. Its ability to solubilize poorly water-soluble drugs makes it indispensable for creating effective delivery systems. In food production, it is occasionally used as a defoaming agent or coating, highlighting its broad safety profile and low toxicity.
Routine Integration
- Synergies: Works exceptionally well with Salicylic Acid by improving its solubility and with Retinol to help deliver the molecule more effectively to target cells.
- Conflicts: There are no known major ingredient conflicts; however, it should be used cautiously in formulations with high levels of other penetration enhancers to avoid over-sensitizing the skin.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel has repeatedly evaluated PEGs and concluded they are safe for use in cosmetics and personal care products. Scientific data indicates that PEG-400 is non-sensitizing and non-toxic when applied to intact skin. However, historical safety concerns regarding 1,4-dioxane contamination are strictly managed today through advanced purification processes, ensuring modern cosmetic-grade PEG-400 meets stringent purity standards. The SCCS notes that while PEGs are safe for the general population, they should not be applied to severely damaged or burned skin, as systemic absorption could occur through an open wound.
Is PEG-400 the same as antifreeze?
No. PEG-400 is frequently confused with ethylene glycol (antifreeze), but they are chemically distinct substances. Polyethylene Glycols have a significantly higher molecular weight and a vastly different safety profile, being non-toxic and widely used in medical and food applications.
Does this ingredient cause acne?
PEG-400 has a comedogenic rating of 0, meaning it is highly unlikely to clog pores or trigger acne. It is frequently found in “oil-free” formulations because it provides moisturizing benefits without the heavy, occlusive nature of traditional oils or waxes.
Can PEG-400 be used on sensitive skin?
Most individuals with sensitive skin tolerate PEG-400 well. Because it can enhance the penetration of other ingredients, it is possible that an irritation response is actually a reaction to an active ingredient (like a fragrance or acid) being delivered more deeply into the skin rather than a reaction to the PEG itself.