Glycerin vs propylene glycol

What is the difference?

An emulsifier helps ingredients mix; a penetration enhancer helps ingredients enter the skin. These are formula jobs, not reasons to assume propylene glycol moisturizes better. For hydration, judge the finished moisturizer rather than declaring a winner from two ingredient names, which is a very small awards ceremony.24

Which should you choose?

For dry skin without a known propylene glycol allergy, either ingredient can serve the water binding part of a moisturizer. Humectants feel less thick and greasy than ingredients such as petroleum jelly that form a coating to reduce moisture loss. A moisturizer can combine both types, so its texture and usefulness depend on more than its humectant.1

Ointments offer a longer lasting protective effect for very dry, thick or scaly areas. Creams are lighter and suit broader application; lotions suit mild dryness and hairy areas. Choose a cream, lotion or ointment you like using, rather than appointing a full bottle to supervise the bathroom.4

What if your skin is sensitive?

Propylene glycol can cause direct irritation as well as allergic sensitization. Contact allergy is relatively uncommon, but it can be more prevalent in people with eczema or otherwise damaged skin. A reaction to a moisturizer does not identify the culprit by itself: fragrances, preservatives and other formula ingredients can also cause problems.234

In a hospital group of 1,979 patients undergoing glycol patch testing, 55 people, or 2.79%, were allergic to propylene glycol. That is a selected group being investigated, not the allergy rate among everyone using moisturizer. Cosmetics were the most common exposure source among those allergic patients, followed by medicines applied to skin.5

How to use a moisturizer containing either

1. 1Wash with warm rather than hot water and a gentle cleanser.
2. 2Rinse well and gently pat dry, leaving skin damp.
3. 3Apply the moisturizer gently, ideally within three minutes of leaving the bath or shower.
4. 4Reapply when skin feels dry. Introduce only one new product at a time so a reaction is easier to trace.

Moisturizers reduce dryness and support the skin barrier. Their benefits are greatest during the first six hours after application, and regular application two to three times daily can be needed to maximize them. Slightly dry skin may need only a light moisturizer at night. These are general moisturizer directions, not a separate schedule for each ingredient.4

When to stop and get help

Stop a moisturizer if contact dermatitis develops, meaning skin inflammation caused by contact with a substance. Seek medical advice for persistent irritation, itching, redness or a rash. A dermatologist can use patch testing to investigate allergy, although propylene glycol reactions can be difficult to distinguish from irritation.124

With confirmed propylene glycol allergy, check complete ingredient lists and avoid products containing it. Ask a pharmacist or doctor to check medicines too, including creams used for eczema. If you use prescription creams, follow your prescriber's layering instructions; some medicines need to go on before moisturizer.12