PEGs on your label: what the letters and numbers mean

Turn over almost any cleanser, lotion or sunscreen and you’ll spot something like PEG-100 stearate, PEG-40 hydrogenated castor oil or ceteareth-20. They’re all members of one family: polyethylene glycols, or PEGs. They’re among the most common ingredients in skin care, and among the most debated. Here’s what they do, what regulators say, and why some people still skip them.

What is a PEG, exactly?

A polyethylene glycol is a chain built from repeating units of a small molecule called ethylene oxide. Chemists call this process ethoxylation, which is why you’ll also see PEG relatives with “-eth-” in their names, like laureth-4 or steareth-2, plus the polysorbates and anything ending in “-oxynol”.

The number after PEG tells you roughly how long the chain is. PEG-4 is a short chain and a runny liquid. PEG-100 or PEG-150 is a long chain and comes as a wax or a solid. The number isn’t a concentration and it isn’t a safety grade; it’s closer to a description of texture and behaviour.

By themselves, PEGs are water-loving. Attach one to a fatty molecule, like stearic acid or castor oil, and you get a molecule with a water-loving head and an oil-loving tail. That combination is what makes them so useful.

What do PEGs do in a product?

PEGs do three main jobs:

• Emulsifiers. An emulsifier keeps oil and water mixed instead of separating into layers. Most creams and lotions are emulsions, and PEG stearates or ceteareths are often what’s holding them together.
• Humectants. A humectant is an ingredient that attracts and holds water. Short-chain PEGs pull moisture into a formula and onto the skin’s surface, which helps a product feel less tight or sticky.
• Solvents and carriers. PEGs help dissolve ingredients that don’t like water, such as fragrance oils, plant extracts or some active ingredients, so they spread evenly through the product.

That last job is where the “PEGs help other ingredients penetrate” idea comes from. It’s partly true. A 2016 review by the Cosmetic Ingredient Review, an expert panel in the United States, summarised experiments in which some PEG esters modestly increased how much of a drug crossed mouse skin, while closely related PEGs did not. It depends on chain length, the other ingredient and the formula. There’s no blanket rule that PEGs open your skin up.

What have regulators and reviewers concluded?

The safety record here is long. A 2005 review published in the journal Toxicology, covering PEGs of a wide range of chain lengths plus their ethers and fatty-acid esters, concluded that they produce little or no skin or eye irritation, have very low toxicity, don’t readily pass through intact skin, and are safe for use in cosmetics as intended.

The same review noted that the few published reports of allergy mostly involved people exposed to PEGs in medicines, or through injured or chronically inflamed skin. On healthy skin, it described the potential for sensitization (the process by which your immune system learns to react to a substance) as negligible.

Health Canada’s position sits in the same place. PEGs are permitted in cosmetics sold here, and the department’s page on ingredient safety addresses the main worry, 1,4-dioxane, directly (more on that below). In the US, the Cosmetic Ingredient Review panel has assessed dozens of PEG ingredients and concluded they’re safe as currently used.

The 1,4-dioxane question, and how Canada handles it

This is the heart of most concerns about PEGs. When ethylene oxide is reacted to make a PEG, a small amount of a by-product called 1,4-dioxane can form. It’s a solvent, not an ingredient anyone adds, and at high exposures it has caused liver and kidney damage and cancer in laboratory animals.

Because it’s a contaminant rather than an intended ingredient, it doesn’t appear on the label. That’s the part people find unsettling, and it’s fair to want to know how it’s controlled:

• Health Canada evaluated exposure to 1,4-dioxane from cosmetic products under Canada’s Chemicals Management Plan and found it to be safe. Its guidance notes that the potential for dioxane in these materials is well known and can be controlled through purification steps, and that it would act to remove a product from sale if unacceptable levels were found. The department points manufacturers to the US FDA’s recommendations.
• The US FDA has since the 1980s encouraged manufacturers to use a technique called vacuum stripping to pull 1,4-dioxane out of raw materials. Its own testing shows the trend: an average of 50 parts per million (ppm) in products sampled in 1981, 19 ppm in 1997, and by 2008, no detectable level in 80 per cent of products tested. In a 2018 survey of children’s products, only 2 per cent were above 10 ppm.
• Europe’s Scientific Committee on Consumer Safety (SCCS), in a 2015 opinion, concluded that a trace level of 10 ppm or less in a finished cosmetic is safe for consumers and should become the target across the industry. That opinion built on the work of an international group of regulators from Brazil, Canada, the European Union, Japan and the United States.

Ten parts per million means ten grams in a tonne of product, and the data suggest most products sit well below it. The 2005 Toxicology review added a sensible caveat: manufacturers must keep removing ethylene oxide and 1,4-dioxane from PEGs, because the safety conclusion depends on those impurities staying low.

Are PEGs a problem for sensitive or damaged skin?

For decades, safety assessments carried a caution that PEGs should not be applied to damaged skin. That came from old reports of kidney toxicity in burn patients treated with antimicrobial creams in a PEG base, absorbed through large areas of severely injured skin.

In 2010 the Cosmetic Ingredient Review panel re-examined the data and removed that caveat, concluding there was no safety concern with using PEGs on damaged skin at cosmetic levels. Still, the practical advice for anyone with a flare of eczema (the itchy, inflamed skin condition) or broken skin is the same for most ingredients: keep the product simple, and if something stings, stop.

Allergy to PEGs is rare but real. It’s more often seen with PEGs in medicines than in skin care, and it can look just like any other contact dermatitis, a rash caused by something touching the skin. If a rash keeps coming back with a particular product and isn’t better two weeks after stopping it, see your doctor or pharmacist.

Why some products advertise “PEG-free”

So why do some products make a point of leaving PEGs out? The reasons are worth taking seriously, even if the evidence doesn’t point to a health risk from normal use:

• Origin. PEGs are made from petrochemicals. Some people prefer plant-derived ingredients for environmental or personal reasons.
• The impurity question. Some people would rather not rely on manufacturers’ purification steps and simply avoid the whole class. That’s a choice, not a mistake.
• Minimalism. People with reactive skin often do best on shorter ingredient lists, and cutting emulsifier-heavy formulas is one way to get there.
• Texture. Products without PEG emulsifiers can feel richer or waxier, which some people like on very dry skin.

What “PEG-free” does not mean is “gentler” or “safer” by default. The replacement ingredients each have their own record, often a shorter one. It’s the whole formula, and your skin’s response to it, that counts.

The takeaway: PEGs are workhorse ingredients with a long, well-documented safety record, considered safe as used by Health Canada, the FDA and Europe’s SCCS. The real issue is a trace impurity that makers are expected to strip out and regulators check for. If you’d rather avoid them, you have options; if you use them, you’re not taking a gamble.