Glycerin, also called glycerol, is a humectant used in moisturisers. When comparing studies, it helps to look beyond the percentage: researchers may measure skin hydration, water loss, or both, often in different formulas and under different conditions.
The following studies offer starting points for a formulation brief. Their results need to be read alongside the products and methods tested.
What the studies measured
| Study discussed below | Main question or comparison |
|---|---|
| Glycerol and petrolatum in an emollient | Skin hydration and water loss with different components |
| Aqueous formulations under occlusion | Hydration under the study’s application conditions |
| Prototypes with different glycerol levels | Short-term hydration and water loss |
| Glycerol preparation in atopic dermatitis | Hydration, barrier measurements, and clinical severity measures |
Hydration and water loss tell you different things
Corneometry uses an electrical measurement to assess hydration near the skin surface. Transepidermal water loss, or TEWL, measures water passing from skin into the surrounding air.
In a randomised crossover study of 51 healthy volunteers with dry skin, researchers compared a complete emollient with its vehicle and versions containing glycerol or petrolatum. They measured effects over 12 hours. The authors attributed improved hydration to glycerol and reduced water loss to petrolatum, with the complete cream combining the effects. One author was affiliated with Pierre Fabre. Read the study.
For a product brief, identify which outcome matters. A favourable hydration reading does not automatically establish every proposed barrier claim.
The surrounding formula affects the experiment
In controlled work with aqueous formulations under occlusion, researchers found that glycerol could promote skin hydration even when the applied formulation had reduced water activity. The study concerns those exposure conditions on volunteers’ forearms; it is not a direct prediction for every lotion or cleanser.
When investigating glycerin concentration, keep the full composition and application conditions available. If several ingredients change at once, the comparison cannot cleanly attribute the outcome to glycerin.
Compare concentrations in the complete formula
A small study in 12 women examined prototypes containing different glycerol levels, including 7%, 10%, and 40%, alongside a glycerol-free control. Measurements at one and five hours distinguished the formulas’ effects on hydration and TEWL. The prototype compositions differed, and the authors were affiliated with L’Oréal. Read the abstract.
The study measured short-term hydration and TEWL. A product comparison also needs to assess texture and the intended use. Select candidate levels around the product’s texture, intended benefit, application, and relevant supplier information. Evaluate the complete prototypes.
Compare spreading and residual tack at agreed time points. For a facial product, include its intended place in the routine, such as layering under sunscreen or makeup. If a texture adjustment changes the composition, check that the intended performance remains.
Keep the claim close to the study
Research on a 20% glycerol preparation in people with atopic dermatitis reported hydration and barrier-measurement improvements without significant between-product differences in several clinical severity measures. That distinction limits the conclusions that can be carried into a general cosmetic story.
For a finished-product study, agree the user group, comparator, application amount, conditions, and primary endpoint. A duration claim needs measurements reaching that duration. Repeated use or performance after washing may require a different design.
For a claim about hydration after washing, include washing in the protocol and measure hydration afterwards.
Sources
- Vaillant and colleagues: Combined effects of glycerol and petrolatum in an emollient cream.
- Alber and colleagues: Water activity, humectants and skin hydration dynamics.
- Caberlotto and colleagues: Simultaneous measurements of skin hydration and water loss.
- Breternitz and colleagues: A glycerol based emollient in atopic dermatitis.
