Glycerin: The Humble Hero Hiding in Almost Every Formula

If skincare ingredients had an awards show, glycerin would never win "Most Exciting". It has no fancy origin story, no celebrity fans and it costs very little. But ask a formulator which hydrator they'd keep if they could only keep one, and a surprising number would say glycerin. Here's why.

What glycerin is

Glycerin (also called glycerol) is a simple, sweet-tasting, syrupy liquid. It's a humectant: it attracts water and holds it. Your skin also makes and uses glycerol naturally, which helps explain why it works so well.

What the research shows

It hydrates and helps the barrier. A well-known review in the British Journal of Dermatology pulls the evidence together: glycerol improves skin hydration, barrier function and the skin's mechanical properties, and it supports barrier repair (Fluhr, Darlenski & Surber, 2008).

Skin has its own glycerol "doors". Skin cells move glycerol through channels called aquaporin-3. In a key study, mice lacking these channels had dry, less elastic skin, and giving them glycerol corrected their hydration, elasticity and barrier recovery (Journal of Experimental Biology summary; Hara-Chikuma & Verkman, 2006). In other words, glycerol isn't just sitting on the surface. Skin actively uses it.

It holds its own against fancier ingredients. In a double-blind study of 197 people with dry, eczema-prone skin, a 20% glycerin cream improved dryness as much as a urea-plus-salt cream, with less stinging (Lodén et al., Acta Dermato-Venereologica, 2002).

It helps irritated skin too. A small study found 2% glycerol helped restore the water-holding capacity of chemically irritated skin (only four volunteers, so treat it as a hint) (Cosmetics & Toiletries).

Glycerin vs the "trendy" hydrators

Remember our hyaluronic acid myth-buster? The study that debunked the "1,000 times its weight" claim found 0.1% HA behaved much like 10% glycerin. Different tools, different jobs: HA gives slip and a surface film at tiny percentages, while glycerin does the heavy lifting on hydration. Many of the best serums use both.

How to formulate with glycerin

• Use level: our glycerin entry lists 3–10%, and up to 20% in occlusive body products. 3–5% is a comfortable starting point for face products.
• Mind the stickiness. Above about 7–10%, many formulas start to feel tacky. Balance it with lighter humectants like Propanediol, Betaine or Sodium PCA.
• Seal it in. Humectants work best with an emollient or occlusive layer on top, so pair glycerin with oils, butters or Squalane, especially in dry or cold weather.
• Build a humectant team: glycerin + Sodium Lactate + Urea (at moisturising levels) mimic parts of the skin's natural moisturising factor.
• Pre-wet your gums. Glycerin is the perfect liquid for dispersing xanthan gum or HA powder before adding water, so they don't clump.

Choosing a grade

For skincare, choose a cosmetic or pharmaceutical grade with a Certificate of Analysis, like Vegetable Glycerin, USP. Plant-derived glycerin is suitable for vegan formulas.

Explore more in Humectants and Hydration & Moisture. Not glamorous, just brilliant.