Ingredient Beauty BenefitsHumectant · Glycerin
Glycerin: the vehicle with only glycerol added did not match the finished formula
In a double-blind crossover study of 51 people with dry skin, the finished emollient reduced transepidermal water loss more than the vehicle and more than the vehicle plus glycerol. Moisturising is the work of a formula, not of one ingredient.
Last checked Sep 16, 2026
Start here
- What it is
The oldest and most widely used moisturising ingredient. Cheap and barely irritating, it is in almost every product.
- What it is used for
Dryness. You will often see it near the top of an ingredient list.
- How it is said to work
It is said to attract water and hold it in the outer layer of skin — closer to helping that layer do its job than to changing it.
There are no numbers and no citations in this box. What has been established, and how far, is below.
At a glance
- In pregnancy
- Not established
- Irritation
- Minimal
- Daytime use
- ✓ Fine
- How well established
- Moderate evidence
- Concentration studied
- Not disclosed
- Length of the studies
- Not disclosed
Not a measurement — reported irritation grouped into five steps. It varies between people.
“Concentration studied” and “Length of the studies” are taken straight from the research on this page. They are not a recommended dose, and the figure for each finding is written out in the text.
This is not how large the effect is but how well confirmed it is. It shows the highest grade among the findings on this page.
Glycerin is the most common and the oldest moisturising ingredient there is. It is a humectant, it is cheap, and it is in almost everything.
Which means its evidence usually shows up inside a formula rather than on its own. The trial below is a rare case of that being demonstrated directly.
What is established
The same ingredient at a different strength, in a different formula, is a different product. These are the conditions the studies used.
The vehicle with glycerol added fell short of the finished formula
A double-blind, four-arm crossover study in 51 healthy volunteers with dry skin (Kligman score 2–3). Four preparations went on the forearms: the finished emollient, the vehicle alone, the vehicle plus glycerol, and the vehicle plus petrolatum.
The finished emollient reduced transepidermal water loss significantly more than the vehicle (P = .0018) and more than the vehicle plus glycerol (P = .0001). Corneometry scores were also significantly higher than vehicle (P < .0001) and than vehicle plus petrolatum (P < .0001).
How you read this matters. The result does not say glycerin is useless; it says glycerin alone does not do what the finished formula does. The authors read the petrolatum component as handling occlusion and the glycerol the water side, working together.
This is why 'contains glycerin' on a label tells you nothing about how a product performs.
- Randomised controlled trial in people · 51 participants · Compared with vehicle (same formula minus the active) · Funding not declared · Endpoint instrument measurement PMID 31532576 · abstract read
How to use it
- Apply while skin is still damp after washing. A humectant needs water to hold.
- Sealing it with something occlusive makes it last longer — that combination is what the trial above demonstrated.
- Higher up the ingredient list means more of it. There is no evidence that more is better.
Cautions
- At high concentrations it feels tacky. How a formula handles that varies by product.
- We found no established data on use during pregnancy.
With a new ingredient, apply a small amount somewhere inconspicuous, such as the inner arm, for two days first. Stop if it reddens or stings.
Related skin concerns
What this article relies on
Unless marked otherwise, a paper was read to the abstract. Only papers whose full text we opened are marked as such.
- PubMed — 미국 국립의학도서관 문헌 데이터베이스National Library of Medicine · Checked on 2026-09-16