If you've ever flipped over a serum bottle and squinted at the ingredient list, you've almost certainly met butylene glycol. It's one of those names that sounds far more alarming than it is — sitting somewhere between "chemical" and "something I definitely can't pronounce." Yet it turns up in cleansers, serums, moisturisers and sunscreens from budget high-street brands right through to luxury dermatologist-led ranges.
So what actually is it, what does it do for your skin, and which REFORM Skincare products contain it? Here's the straightforward answer.
What Is Butylene Glycol?
Butylene glycol (also written as 1,3-butanediol, and often shortened to BG) is a colourless, slightly syrupy liquid. It belongs to a family of ingredients called glycols, alongside the propylene glycol and pentylene glycol you'll see listed nearby on many labels.
In the UK and across the EU, butylene glycol is an approved cosmetic ingredient. The EU's CosIng database lists its official functions as humectant, solvent, skin conditioning agent and viscosity controller — in other words, it's a multi-tasking workhorse rather than a headline "active."
One important point: despite the "-ol" ending, butylene glycol is not the kind of alcohol that dries out or strips your skin. That reputation belongs to ethanol and denatured alcohol. Butylene glycol behaves much more like glycerin — it holds onto water rather than pulling it out.
What Does It Do for Skin?
It's a humectant — it draws in and holds moisture
This is butylene glycol's headline job. Humectants attract water from the air and from deeper layers of the skin, helping to keep the surface hydrated. A 2023 study published in the International Journal of Cosmetic Science found that humectants — including butylene glycol — significantly improved skin hydration and reduced transepidermal water loss (the rate at which moisture escapes through the skin) over an eight-hour period.
In practice, that means skin that feels softer and more comfortable, and a complexion that looks plumper and less lined. Hydration is the foundation of a healthy skin barrier, so this isn't a trivial benefit.
It's a solvent — it keeps formulas stable and effective
Many of the ingredients that actually change your skin — vitamin C, salicylic acid, retinol, niacinamide — are notoriously difficult to dissolve. Butylene glycol acts as a solvent, keeping them evenly dispersed through a formula rather than separating, crystallising or going gritty.
Without a solvent like butylene glycol, your vitamin C serum might arrive as a grainy, unstable mess. It's a supporting player that makes the stars possible.
It's a penetration enhancer — it helps actives get where they're needed
Butylene glycol helps other ingredients spread more evenly across the skin and improves their absorption. In a well-built formula, that means the actives you're paying for are delivered more efficiently rather than sitting on the surface.
It improves texture and feel
Because it's also a viscosity controller, butylene glycol helps give products a pleasant slip and spreadability. It's part of the reason a serum glides rather than drags, and why a gel feels light rather than tacky.
Is it safe?
The evidence is reassuring. A safety assessment by the Cosmetic Ingredient Review (CIR) expert panel concluded that butylene glycol is safe as currently used in cosmetics. Human patch testing has shown a very low order of skin irritation, and a repeated insult patch test found no evidence of skin sensitisation.
It's also used as a food additive in some markets and is approved by Ecocert for natural formulations. If you see "petroleum-derived" alongside its name online, note that's an origin point, not a safety verdict — plenty of entirely benign cosmetic ingredients share it.
The honest caveat: a small number of people with very reactive or sensitive skin report irritation, and some acne-prone users report congestion. This is uncommon, but if you know your skin reacts to glycols, patch test first.
Which REFORM Skincare Products Contain Butylene Glycol?
REFORM Skincare is a dermatologist-formulated, science-led range available in the UK, built around proven actives. Butylene glycol appears across several of its formulas, typically sitting high in the ingredient list as a solvent and humectant.
HYAL • Vitamin C + E Serum — the most prominent inclusion. Butylene glycol appears early in the ingredient list, working alongside propylene glycol and ethoxydiglycol to keep the vitamin C (ascorbic acid), hyaluronic acid and panthenol stable and evenly delivered. Given how notoriously unstable vitamin C serums are, this is exactly the kind of formula where a solvent system earns its place.
Retinol 1% Crème — butylene glycol appears in the ingredient list alongside panthenol, ceramides and vitamin E. Here it supports hydration and spreadability in a rich night treatment, while the ceramide and cholesterol complex helps offset retinol's drying effects.
Anti-Blemish Kit — the three-step routine built around salicylic acid, mandelic acid and glycolic acid. Its cleanser and gel steps list glycol-based humectants (propanediol and pentylene glycol) in the solvent and hydration roles, supporting the acid actives while keeping the barrier comfortable.
Other formulas — several cleansers, gels and moisturisers in the REFORM range use glycol-family humectants and solvents throughout, which is typical of well-formulated, active-led skincare. Ingredient lists can and do change, so for the definitive answer on any specific product, always check the label on the packaging you receive — or the current list on REFORM's own site.
Why Brands Use It
If you're wondering why butylene glycol is so widespread, the answer is simple: it's one of the few ingredients that's simultaneously a good humectant, an effective solvent, a texture improver and a penetration enhancer, with a long-established safety profile and low irritation potential.
For an active-led brand like REFORM, whose formulas centre on vitamin C, retinol and acids, that combination is genuinely useful. The actives get the credit — but they need a delivery system, and butylene glycol is a reliable one.
The Bottom Line
Butylene glycol is a safe, well-tolerated humectant and solvent that draws moisture into the skin, keeps unstable actives dissolved, and helps formulas spread and absorb better. It isn't a miracle ingredient and it isn't a villain — it's the scaffolding that lets other ingredients do their job.
If it appears in your REFORM serum or crème, that's a good sign the formula has been built with stability and hydration in mind. The only real caveat is personal sensitivity: if your skin is reactive to glycols, patch test as you would with anything new.
This article is for general information only and is not medical advice. If you have a diagnosed skin condition or a known sensitivity to glycols, consult a GP, dermatologist or qualified skincare professional before introducing new products.
