Propylene glycol (INCI: Propylene Glycol, or 1,2-propanediol) is a clear, scentless, water-soluble liquid alcohol used widely across cosmetics, pharmaceuticals, and foods. Rather than serving a single purpose in skincare, it acts as a multitasker: functioning as a humectant, solvent, penetration enhancer, and texture modifier. Typically present at concentrations between 1% and 10% in leave-on products, it helps deliver active ingredients efficiently while keeping formulas stable and pleasant to use.
According to the Cosmetic Ingredient Review (CIR) safety panel, its primary functions include:
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Dissolving active ingredients: Allows water-insoluble compounds to integrate seamlessly into aqueous formulas.
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Attracting moisture: Functions as a humectant to draw water into the upper layers of the skin.
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Enhancing texture: Improves product glide, spreadability, and consistency.
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Ensuring stability: Protects formulations against separation across temperature fluctuations.
Safety and UK Regulatory Status
The CIR Expert Panel considers propylene glycol safe for cosmetic use at current concentrations, rating it as generally non-toxic, non-carcinogenic, and non-sensitising in clinical trials.
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The "Antifreeze" Myth: Whilst industrial-grade propylene glycol is used in anti-freeze, cosmetic and food-grade variants are highly purified, distinct specifications. The comparison holds no toxicological relevance for skincare products.
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Skin Tolerance: Propylene glycol carries a low comedogenicity rating (0) and low irritancy scores in standard assessments. Irritation or allergic contact dermatitis remains uncommon, typically occurring only at high concentrations (above 50%) or on broken, severely compromised skin. True allergy rates in the general population sit at roughly 1–2%.
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UK Cosmetic Law: Under retained EU Cosmetic Regulation in UK law, propylene glycol is permitted in adult skincare without a strict concentration ceiling, though restrictions apply to products formulated for children under three years old.
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Sensitivity Advice: If you have eczema or a damaged skin barrier, glycol-heavy formulas may cause mild stinging. Patch-testing on the inner forearm for 48 hours is recommended. If a reaction occurs, discontinue use and consult a pharmacist, GP, or dermatologist.
Key Benefits for Skin
1. Superior Hydration (Humectant)
Propylene glycol has a strong affinity for water. By attracting moisture to the stratum corneum and binding it there, it leaves the complexion looking plumper, smoother, and less prone to flaking. It provides a cost-effective, highly reliable way to boost a moisturizer's hydrating power.
2. Enhanced Active Delivery (Penetration Enhancer)
Propylene glycol temporarily alters the skin barrier's lipid bilayer to help key ingredients cross more effectively. Research, including a 2024 study in the International Journal of Molecular Sciences, demonstrates that it localises at the bilayer interface to occupy lipid–water hydrogen-bonding sites. This temporary shift in permeability allows active ingredients like vitamin C, retinol, and niacinamide to work far more effectively.
3. Texture and Formula Stability
As a solvent and viscosity modifier, it prevents emulsions from separating and delivers a smooth, lightweight feel. It also enhances freeze-thaw stability, ensuring serums retain their consistency even when stored in cold bathrooms or warm travel bags.
Which REFORM Skincare Products Contain Propylene Glycol?
REFORM Skincare is a doctor-led cosmeceutical range utilizing high concentrations of antioxidants and acids. The brand transparently lists propylene glycol on its product packaging and official website.
Spotlight: HYAL • Vitamin C + E Serum
In REFORM’s flagship antioxidant serum, propylene glycol features third on the INCI list (following aqua and ascorbic acid). Vitamin C is notoriously unstable and difficult to transport through the stratum corneum; pairing it with propylene glycol and ethoxydiglycol ensures maximum stability and skin delivery. On its platform, REFORM highlights it as a "hydrating solvent that improves ingredient delivery while helping maintain skin hydration."
Spotting Propylene Glycol Across the Range
Formulations adapt as product lines expand (such as the Skin Barrier Repair Cream and SPF 50+ Invisible Mist Spray). Use this general guide when reviewing labels:
| Product Type | Likely Role of Propylene Glycol | Frequency |
| Vitamin C & Antioxidant Serums | Solvent and penetration enhancer | Very High |
| Gel Treatments (e.g., Phyto Botanical, Vitamin B5) | Texture, slip, and hydration | High |
| Lightweight Moisturisers | Secondary humectant | Moderate |
| Rich Creams & Oils | Emulsification / texture support | Low |
To verify a specific product, check the online ingredient panel where Propylene Glycol will be explicitly named.
Propylene glycol remains one of the most effective supporting ingredients in modern skincare. It hydrates, stabilises, and helps premium active ingredients penetrate where they are needed most. Supported by a strong safety profile and clear regulatory status in the UK, it is a primary example of how a functional base ingredient enables active formulations to perform at their best.
