In the "toolbox" of cosmetic formulators, polyethylene glycol (PEG) is almost an unavoidable name. From a lip balm to a bottle of cleansing oil, from serum to shower gel, PEG series raw materials have become the "universal solvent and skeleton" of the modern cosmetics industry with their unique properties of gentleness, stability, hydrophilic and lipophilic compatibility. However, the controversy over PEG is equally persistent - issues such as 1,4-dioxane residue, skin permeability, and sensitive skin tolerance have deterred many brands and consumers.
This article will systematically dismantle the chemical nature, grading system, safety evaluation, solubility optimization techniques, formulation application strategies, and compliance and trends of polyethylene glycol in cosmetics from the perspective of a cosmetic formulator and RA, providing a practical manual that can be directly implemented for R&D, procurement, registration, and brand teams.

1. What is Polyethylene Glycol (PEG)?

Polyethylene glycol is a linear polyether made of catalytic polymerization of ethylene oxide (EO), and its general structure is:

HO–(CH₂CH₂O)ₙ–H

The cosmetics industry is named after its average molecular weight, such as:

• PEG-4 ≈ Average molecular weight 200 (liquid)

• PEG-8 ≈ 400(Liquid)

• PEG-32 ≈ 1500(Semi-solid state)

• PEG-75 ≈ 3350(waxy)

• PEG-150 ≈ 6000(Solid wax)

⚠️ Note the numbers in the INCI naming = EO Number of units,And the numbers in industrial product naming (e.g., PEG-400, PEG-4000). = Average molecular weight,The expression systems of the two are different, and it is important to check clearly when purchasing and formulating。

2. The core physical and chemical properties of PEG

The reason why polyethylene glycol can play an all-rounder role in cosmetics is due to its unique combination of physicochemicals:

It is the combination of "water and oil parents + extremely wide compatibility + hypoallergenic and low irritation" that makes PEG ubiquitous in lotions, creams, gels, cleanses, and makeup.

3. The core function of PEG in cosmetics

1. Solvent / Co-solvent

Low molecular weight PEG (PEG-200 ~ PEG-600) is an excellent solvent for poorly soluble actives (e.g., salicylic acid, vitamin E, coenzyme Q10, plant extracts) and is often used as a bridging co-solvent for water/alcohol systems.
2. Humectant
Medium molecular weight varieties such as PEG-8 and PEG-32 can form a soft film on the surface of the skin, providing a lightweight, non-sticky moisturizing feel, especially suitable for summer formulas and men's skincare products.
3. Thickener / Base
PEG-4000, PEG-6000 and other high molecular weight varieties are waxy or solid, which can be used as: - Skeleton wax for lipstick / lip gloss - Consistency modifier for cream - Solid base for makeup remover - Structural agent for toothpaste
4. Emulsification aid and stabilizer
PEGylated derivatives (e.g., PEG-100 Stearate, PEG-40 Hydrogenated Castor Oil) are used to give the system excellent emulsification stability and washability.
5. Controlled release and film formation
High molecular weight PEG forms a softening film in masks, patches, and makeup remover wipes, improving spreadability and skin feel.
6. Formulation "Texture Modifier"
PEG can fine-tune the product: - Slippery feel - Brushing feel - Extensibility - Residual feeling after drying
This is the value of "detail workmanship" that is difficult to replace with other polyols.

4. Grading system and selection of cosmetic grade PEG

1. By form

2. According to the quality grade

• Industrial – Not for use in cosmetics

• Cosmetic Grade – INCI compliant, low heavy metals, low EO/dioxane residue

• Pharmaceutical grade (USP/EP/NF) — the most stringent requirements for cosmeceutical and aesthetic grade skincare

• Food Grade (FCC) – can be used in lip products (oral contact risk)

✅ Formulator's selection suggestions: Lips, eyes, infants, medical beauty products → Prefer USP/EP grade General skin care, cleansing, makeup, → cosmetics grade is sufficient, but the supplier needs to provide 1,4-dioxane and EO residue test reports

3. By EO residue and dioxane control

International high-quality suppliers usually provide "Low 1,4-Dioxane" series, and the residue is usually controlled at: - ≤ 10 ppm (EU, China compliance bottom line) - ≤ 2 ppm (high-end brand internal control line) - < 1 ppm (recommended for medical aesthetics/baby products)

5.PEG Security evaluation: scientific facts vs online rumors

PEG is one of the most "controversial" ingredients in the cosmetics industry. We clarify item by item:
1. Is PEG inherently toxic?
Nope. The evaluation of many authorities such as CIR (Cosmetic Ingredient Review), SCCS (European Union Committee for the Safety of Cosmetics), ECHA, FDA, etc. believes that PEG and its common derivatives are safe for use in cosmetics according to regulations. Its oral LD50 is generally > 30 g/kg, and transcutaneous irritation is very low.
2. Does PEG break the skin barrier?
On normal intact skin, PEG is barely absorbed and does not "open" the stratum corneum. The so-called "PEG increases skin penetration" mainly comes from early observations of broken skin (such as patients with severe burns), which is completely different from the daily intact skin scenario.
3. 1,4-dioxane problem
1,4-dioxane is a by-product impurity that can be produced during the production of PEG with PEG derivatives (PEG/PPG-, Polysorbate, SLES) and is classified by IARC as Category 2B (possibly carcinogenic).
✅ Key takeaway: This is a production process carryover issue, not a property issue of PEG itself. Compliance strategies include: - Selection of suppliers for dioxane removal through the "vacuum stripping" process - Strict batch testing of 1,4-dioxane levels - China, the European Union, and the US FDA have set limits (≤10 ppm) - Internal controls of ≤ 2 ppm are recommended for high-end products
4. Ethylene oxide (EO) residue
EO is the starting ingredient for PEG synthesis and residues need to be controlled: - General requirement ≤ 1 ppm - Recommended ≤ 0.5 ppm for infant products
5. Allergenicity
PEG-only sensitization is very low, and contact dermatitis is mostly reported in the literature associated with exposure to derivatives (e.g., impurities of PEG-100 Stearate) or broken skin. In daily skincare scenarios, PEG is a relatively safe excipient for sensitive skin.
6. Controversy in the context of "clean beauty"
Some brands take the initiative to declare "PEG-Free" out of market positioning, but this is more of a marketing strategy than a scientific conclusion. Formulators should make technical judgments based on efficacy and safety data, rather than being driven by public opinion.

6. PEG solubility optimization practice

The solubility of PEG may seem simple, but in fact, it often "rollovers" in formulations. Here are some common problems and solutions:

Problem 1: Low temperature precipitation / turbidity

High molecular weight PEG (PEG-4000+) decreases in solubility at low temperatures and is prone to crystallization and precipitation in aqueous phases.

Solution: - Heat up to 60~70°C to completely dissolve before emulsification - Combine with PEG-400 / propylene glycol / butanediol to reduce crystallization tendency - Choose a model with a narrow molecular weight distribution to reduce precipitation temperature drift
Problem 2: Conflict with electrolytes
High concentrations of salt, acidic systems can lead to PEG "salting".
Solution: - Control electrolyte concentration < 2% - Replace pure PEG with PEG derivatives such as PEG-150 Distearate - Add chelator stabilization system
Problem 3: Incompatibility with silicone oil
PEG and silicone oil (Dimethicone) have large polar differences, and direct coexistence will lead to layering.
Solution: - Use PEG-Dimethican (silicone oil PEGylated derivative) as a compatible bridge - Design a W/Si or Si/W emulsification system
Problem 4: Incompatibility with cationic surfactants
High molecular weight PEG compounds precipitation with certain cations (such as quaternary ammonium salts) at high concentrations.
Solution: - Reduce PEG dosage - Switch to nonionic PEG derivatives - Adjust dosing order to avoid localized high concentrations
Problem 5: Risk of active degradation
PEG can produce trace amounts of peroxide (Peroxide) when stored for a long time or at high temperatures, causing oxidative damage to sensitive actives such as vitamin A, retinol, and coenzyme Q10.
Solution: - Select "Low Peroxide" grade PEG - Add antioxidants (BHT, tocopherol) - Nitrogen-filled packaging, store away from light

7. Typical formula application cases

Case 1: Oil-in-Water (O/W) moisturizer

 • PEG-100 Stearate: Emulsifier, 2.0%

• PEG-400: Co-Solvent + Moisturizing, 5.0%

• PEG-8: Light Moisturizing, 2.0%

Case 2: Waterless makeup remover

• PEG-6000: Solid State Skeleton, 40%

• PEG-400: Solvent phase, 25%

• PEG-20 Glyceryl Stearate: Emulsification Aid, 8%

Case 3: Highly Moisturizing Gel

• PEG-32: Moisturizing workhorse, 5%

• Carbomer: thickening

• Butylene glycol + glycerin: Assists in hydration

Case 4: Lipstick (USP grade PEG)

• PEG-3350 + PEG-1000: Base skeleton, 60% total

• USP/NF grade for oral contact safety

Case 5: Medical Aesthetic Restoration Essence

• PEG-400 (low dioxane, ≤ 1 ppm): active solvent

• Combined with panthenol, ceramides, ectoine

VIII. Compliance and Regulatory Requirements (2026 Update)

china

• Catalogue of Used Cosmetic Ingredients (2021 Edition & Update) – all included in the PEG series
• NMPA requires 1,4-dioxane ≤ 30 ppm (10 ppm ≤ some product types)
• Infant cosmetics are subject to stricter limits

European Union
• CosIng database indexed, regulated by EC 1223/2009
• 1,4-dioxane limit of 10 ppm
• The SCCS considers PEG derivatives on an ongoing basis

United States
• FDA considers PEGs to be GRAS (Generally Recognized As Safe)
• California Prop 65:1,4-dioxane requires a warning (e.g., exceeding threshold)
• Many states have passed legislation to limit dioxane levels

South Korea / Japan
• The use of PEG is allowed in MFDS in South Korea and the Ministry of Health, Labour and Welfare in Japan
• Japan has a "pre-existing raw material" limit for some PEG derivatives
✅ Cross-border brand recommendations: Uniformly implement the strictest standards (1,4-dioxane ≤ 2 ppm) and require suppliers to issue multi-country compliance statements.

10. Precautions for storage and handling

• Storage conditions: cool and dry place, away from light, temperature ≤ 30°C

• Packing: HDPE drum or aluminum drum, lined with PE bag

• Shelf life: usually 24 months

• Melting Operation: High molecular weight PEG heated ≤ 80°C to avoid oxidation and peroxide production

• Avoid long-term exposure to high temperatures: prevent oxidative degradation

• Nitrogen Protection: Recommended for low peroxide levels

• Compatibility contraindications: strong oxidants, strong acids and alkalis, high concentrations of some cationic surfactants

 Trends and outlook for 2026
1. Adoption of ultra-low dioxane processes – < 1 ppm is a new baseline for high-end brands

2. Rise of Bio-based PEGs — Replacing petrochemical sources with bio-based EOs reduces carbon footprint

3. PEG-Free Marketing vs. Science Back — More and more authorities are coming forward to correct their names

4. Refinement of PEG derivatives — PEG-Dimethicone, PEG-Stearate series narrow distribution

5. Sustainability Certification Premium – Rising demand for RSPO MB/SG grade PEG derivatives

6. Digital COA — e-certificate and blockchain traceability into the supply chain of large brands

7. Fusion of aesthetics and cosmeceuticals — USP-grade PEG is used in functional skincare to increase the ratio

8. Stricter environmental supervision - microplastics and biodegradability have entered the EU's next round of deliberations

FAQs

Q1: Is PEG really harmful? Based on the evaluation of authoritative institutions, compliant cosmetic grade PEG is safe for intact skin under normal use. The controversy over the so-called "harmful" comes mainly from process impurities (1,4-dioxane) rather than from PEG itself.

Q2: Can sensitive skin use PEG-containing products? Yes, but it is recommended to choose a formula with a low impurity level and low concentration, and avoid long-term use on broken skin.

Q3: Can pregnant women use PEG-containing skincare products? PEG is extremely low transdermal absorption and there is currently no evidence of risk in pregnant women with daily use. If you have concerns, you can choose USP/EP grade.

Q4: What is the difference between PEG and PPG? PEG is a polymer of ethylene oxide (hydrophilic) and PPG is a polymer of propylene oxide (more hydrophobic). The two are often used together to form a PEG/PPG copolymer.

Q5: Are PEG-Free products necessarily safer? Not necessarily. PEG-Free is a marketing positioning, but its alternative ingredients are not necessarily milder or more environmentally friendly. Safety depends on the overall formulation, not on a single ingredient.

Q6: How can I verify dioxane content in a COA? Suppliers are required to provide a special report on 1,4-dioxane for GC-MS detection, focusing on detection methodology (LOD/LOQ) and limits.

Epilogue
Polyethylene glycol (PEG) is an indispensable "molecular engineer" in the modern cosmetics industry: it is gentle, stable and highly malleable, and plays a variety of roles in formulations as a solvent, moisturizer, skeleton, emulsification aid, and skin conditioning. The real question around PEG is not "whether to use it" but "what grade, what impurities to control, and how to scientifically assess safety".

As we enter 2026, classic ingredients like PEG are serving the next generation of cosmetic innovation in a greener, safer, and more transparent way with the proliferation of bio-based PEG, ultra-low dioxane processes, sustainable certifications, and digital traceability. For formulators and brands, instead of being coerced by online public opinion, it is better to return to science and data and choose high-quality PEG raw materials that are truly compliant, traceable, and explainable.