57-55-6

📋 Quick facts

Description: 57-55-6 — 57-55-6. Formula: C3H8O2. MW: 76.09. IUPAC: propane-1,2-diol.

Quick Facts:

• Category: other
• Also Known As: Propylene glycol

Proven Benefits At A Glance:

• 57-55-6 is the chemical identifier for propylene glycol (PG), a common ingredient in cosmetics and pharmaceuticals
• About 2.79% of patch-tested patients showed allergic contact dermatitis to propylene glycol
• When propylene glycol is used in cosmetics, the face and hands are the most common areas affected by allergic reactions
• Short-term exposure to propylene glycol mist can cause eye and throat irritation in some people, though serious airway effects are rare

⚗️ Chemical Overview

Propylene glycol is a synthetic liquid substance that absorbs water. Propylene glycol is also used to make polyester compounds, and as a base for deicing solutions. Propylene glycol is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food. The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is “generally recognized as safe” for use in food. It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products. It is a solvent for food colors and flavors, and in the paint and plastics industries. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. Other names for propylene glycol are 1,2-dihydroxypropane, 1,2-propanediol, methyl glycol, and trimethyl glycol. Propylene glycol is clear, colorless, slightly syrupy liquid at room temperature. It may exist in air in the vapor form, although propylene glycol must be heated or briskly shaken to produce a vapor. Propylene glycol is practically odorless and tasteless. Thick odorless colorless liquid. Mixes with water. (USCG, 1999) Propane-1,2-diol is the simplest member of the class of propane-1,2-diols, consisting of propane in which a hydrogen at position 1 and a hydrogen at position 2 are substituted by hydroxy groups. A colourless, viscous, hygroscopic, low-melting (59C) and high-boiling (188C) liquid with low toxicity, it is used as a solvent, emulsifying agent, and antifreeze. It has a role as a protic solvent, an allergen, a mouse metabolite and a human xenobiotic metabolite. It is a glycol and a member of propane-1,2-diols.

Source(s): ChEBI, Agency for Toxic Substances and Disease Registry (ATSDR), CAMEO Chemicals, via PubChem

📊 Comedogenicity

🛡️ Safety rating

Safety tier is a starting heuristic from regulatory status and comedogenic rating, not a dermatological verdict — see our Terms for the full disclaimer. Research confidence reflects how many real cited studies back this ingredient, not the strength of their findings.

🌍 Regulatory Status

💧 Skin Type Compatibility

⚠️ Don’t Combine With

📚 Research & Evidence

🔬 The Science

Propylene glycol (57-55-6) is a widely used humectant—a substance that helps products absorb and retain moisture—found in cosmetics, pharmaceuticals, foods, and industrial applications like de-icing fluids and paints (Occup Environ Med). #1: Allergic contact dermatitis risk is real but uncommon. When researchers patch-tested nearly 2,000 patients with propylene glycol, about 2.79% developed an allergic reaction (Contact Dermatitis). The concentration matters: higher concentrations detected more cases, with 7.82% reactivity at 100% concentration compared to just 1.06% at 5% (Contact Dermatitis). For people who do develop an allergy, dermatitis appears mainly on the face and hands, and cosmetics are the most common culprit (67.3% of cases), followed by topical medications (Contact Dermatitis).

#2: Cross-reactivity with similar glycol ingredients appears limited. Some people allergic to pentylene glycol (another glycol used in skincare) also reacted to propylene glycol, but this occurred in only a minority of cases; caprylyl glycol showed even less overlap (Contact Dermatitis). #3: Acute irritation from propylene glycol mist exposure is possible but typically mild and temporary. When non-asthmatic volunteers were exposed to propylene glycol mist in an aircraft simulator for one minute, most experienced temporary eye and throat irritation, and tear film stability (how long tears stay on the eye) decreased (Occup Environ Med). A small number developed cough and minor airway obstruction, but these effects were not severe and no systemic (whole-body) symptoms occurred (Occup Environ Med).

This reflects extreme exposure conditions—normal skincare use would involve much lower concentrations.

📄 Related Research

Matched by search — not necessarily verified support for every statement above.

• Kanokrungsee S et al. (2026). Contact Allergy and Allergic Contact Dermatitis From Propylene Glycol and Related Glycols: Cosmetic Skin Sensitisers After All?. Contact Dermatitis.
• Wieslander G et al. (2001). Experimental exposure to propylene glycol mist in aviation emergency training: acute ocular and respiratory effects. Occup Environ Med.

🧴 Products Containing 57-55-6