Propylene Glycol: The Workhorse Humectant, and When It Bothers Skin

Propylene glycol helps skincare hold moisture and carry active ingredients. A plain-English UK guide to what it does, irritation versus true allergy, and who should keep an eye on it.

What it is

Propylene glycol, often shortened to PG on labels, is one of the most widely used ingredients in personal care. It is a clear, slightly syrupy liquid that does two main jobs at once. First, it is a humectant, which means it draws in and holds water, helping a product stay moist and helping your skin feel hydrated rather than dry. Second, it is a solvent and carrier, which means it dissolves other ingredients and helps them spread evenly and penetrate the surface of the skin.

Because it is cheap, stable, mixes well with both water and oils, and has a long history of safe use, propylene glycol turns up almost everywhere: skincare, makeup, deodorants, haircare, and many medicines. It is also used in food and as a solvent for flavourings and colours, which is one reason it has been studied so extensively.

Why it is used in skincare and household products

Formulators reach for propylene glycol because it quietly solves several problems. It stops water-based products drying out on the shelf or in an opened jar. It keeps textures smooth and pleasant. It helps active ingredients dissolve so they are evenly distributed rather than clumping. And it can improve how well certain ingredients pass into the upper layers of skin, which is useful in both cosmetics and topical medicines.

In household and personal products beyond skincare, you will find it in deodorants and antiperspirants, some wet wipes, hand sanitisers and cleaning products, again because it holds moisture and carries other ingredients well.

The UK and EU rules

Propylene glycol is permitted for use in cosmetics in the UK and the EU. It is not one of the 26 named fragrance allergens, it is not a banned substance, and it is not subject to the kind of leave-on restriction that applies to certain preservatives. Its safety has been reviewed by cosmetic safety bodies, and it is regarded as safe for use in the concentrations normally found in products.

That regulatory approval is a general statement about the population, not a personal guarantee. A substance can be safe for the vast majority and still cause irritation or allergy in some individuals. UK and EU labelling rules require propylene glycol to be listed by its INCI name in the ingredients, so anyone avoiding it can find it.

Who reacts, and why

There are two separate things that can happen, and it helps to keep them apart.

The first is simple irritation. Propylene glycol at higher concentrations can sting or feel tight on skin that is already compromised, for example eczema-prone, cracked or freshly exfoliated skin. This is not an allergy. It is a direct effect, more likely in leave-on products where the ingredient sits on the skin rather than being rinsed away.

The second is a true contact allergy, where the immune system becomes sensitised and reacts on later exposure. This is genuinely less common with propylene glycol than with, say, fragrance or the preservative methylisothiazolinone, but it does happen. People with eczema or a damaged skin barrier are more prone to becoming sensitised because more of the substance gets through. Reactions of this type are typically delayed, appearing a day or two after contact as itching and redness.

Patch testing by a dermatology clinic is the reliable way to tell irritation from allergy, and propylene glycol is included in some standard test panels.

How to spot it on a label

On an ingredients list, look for Propylene Glycol, the INCI name it is almost always listed under. You may also see the chemical names 1,2-Propanediol or Propane-1,2-diol, or the short form PG. In leave-on products it often appears fairly high up the list, reflecting how much is used.

Because it is a workhorse ingredient, it hides in a very wide range of products: moisturisers, serums, foundations and other makeup, deodorants, and some medicated creams and ointments from the pharmacy. If you are trying to avoid it, it is worth checking medicine leaflets and toiletries as well as obvious skincare.

A balanced, honest take

Propylene glycol occasionally gets bundled in with ingredients that people worry about online, sometimes because its name resembles ethylene glycol, a toxic antifreeze component that is a completely different chemical. That mix-up has fuelled some unnecessary alarm. The mainstream scientific and regulatory view is that propylene glycol is low in toxicity and safe at the levels used in cosmetics.

At the same time, it is fair to say it is not perfectly inert for everyone. A real minority of people, especially those with eczema or very reactive skin, do find it irritating or, less often, are allergic to it. Both things can be true at once: safe for the population, and still a genuine trigger for some individuals. The sensible position is neither to fear it nor to dismiss a personal reaction to it.

What to do if you’re avoiding it

If you suspect propylene glycol is one of your triggers, the practical steps are calm and simple. Note down the products that seem to sting or flare your skin and check whether propylene glycol appears in them. Consider switching to products that use alternative humectants such as glycerin, butylene glycol or pentylene glycol, while accepting that these can occasionally irritate too. When trying anything new, patch test it on a small area of inner forearm for a few days before using it more widely.

If reactions keep happening across many products, or you are not sure whether you are dealing with irritation or a true allergy, see your GP, a pharmacist, or ask about a dermatology referral for patch testing. This is a guide to reading labels, not a substitute for medical advice.

Check products against your list

To check a product, INCIBeauty lets you look up a product and read plain-language notes on each ingredient, with a community that rates them, and a free analyser like Skincarisma lets you paste a product at your desk and see propylene glycol flagged in the ingredient list. These rate a product on general criteria rather than against your own list.

Once you know what you are screening for, a personal-list app like ClearaScan lets you save propylene glycol once and scan any product to flag only your triggers. It also keeps a Reaction Journal for flare-ups, a shared Care Circle so family or carers can scan for you, and a Trusted Products list for items you have cleared, and it is currently in early access. (Disclosure: our editor co-founded ClearaScan, and we are not paid to mention the others.)

Written and reviewed by the Sensitive Skin Lab editorial team.