Glycerin — The Most Researched Humectant in Cosmetics

Glycerin — the quiet hero of cosmetics

Glycerin (listed as Glycerin in INCI nomenclature) is probably the most widely used cosmetic ingredient in the world — second only to water. You'll find it in creams, serums, shampoos, body lotions, lip balms and thousands of other products. Yet despite this ubiquity, it rarely makes headlines or drives marketing campaigns.

Why? Because glycerin is "boring" — at least from a marketing point of view. It isn't exotic, it doesn't come from a rare Amazonian plant, and it has no captivating backstory. What it is, however, is remarkably effective, safe and well-researched. And perhaps that should convince us far more than any trendy name.

What exactly is glycerin?

Glycerin (glycerol) is a simple trihydric alcohol — a colourless, odourless, slightly sweet liquid with a thick, syrupy consistency. It occurs naturally in the skin as part of the natural moisturising factor (NMF) and plays a key role in keeping the epidermis properly hydrated.

In cosmetics, glycerin works primarily as a humectant — a substance that draws water from its surroundings and binds it within the skin. A single glycerin molecule can bind several water molecules, making it one of the most efficient moisturisers available.

Why is glycerin so effective?

Glycerin's effectiveness is backed by decades of scientific research. Here are the key mechanisms behind how it works:

• Attracting and binding water: glycerin is hygroscopic — it draws moisture from both the deeper layers of the skin and the surrounding air, holding it within the stratum corneum
• Strengthening the skin barrier: studies have shown that glycerin supports the hydrolipid barrier and speeds the healing of minor epidermal damage
• Improving elasticity: well-hydrated skin is more elastic and more resistant to mechanical irritation
• Protective action: glycerin soothes irritation and shields the skin from external aggressors

Importantly, glycerin is non-allergenic and extremely rarely triggers adverse reactions, which makes it safe even for the most sensitive skin, including the skin of newborns.

Optimal glycerin concentrations in cosmetics

The concentration of glycerin in a product has a significant impact on both its effectiveness and how comfortable it feels to use:

• 2–5%: the minimum effective dose — subtle hydration and a light texture
• 5–10%: the optimal concentration in most everyday products; a good balance between effectiveness and comfort
• 10–20%: intensive hydration, used in products for very dry skin; may leave a sticky feel
• Above 20%: a very high concentration that can paradoxically dry out the skin in arid climates, drawing water from the deeper layers of the epidermis rather than from the air

The optimal concentration is usually 5–10%, which delivers effective hydration without a sticky finish. Unfortunately, exact concentrations are rarely stated on packaging — the best clue is the position on the INCI list.

Glycerin's position on the INCI list — what does it tell you?

Ingredients on an INCI list are given in descending order of concentration (for ingredients present above 1%). Glycerin's position on that list offers useful clues:

• Position 2–3 (right after Aqua): a high concentration (likely 5–15%), indicating an intensively hydrating product
• Position 4–6: a moderate concentration (around 3–8%), standard for most cosmetics
• Position 7 and beyond: a low concentration (below 3%), where glycerin plays a secondary role

It's worth checking this using our ingredient search — the INCI position is one of the few ways to estimate how much of an ingredient a product actually contains.

Glycerin and dry climates — legitimate concerns

One of the most frequently raised objections to glycerin is its potentially unfavourable behaviour in dry climates. Are these concerns justified?

As a humectant, glycerin draws water from its surroundings. When air humidity is very low (below 30–40%), glycerin can start pulling water from the deeper layers of the skin instead of from the air, which paradoxically leads to increased dehydration.

However, this problem mainly applies to:

• Very high glycerin concentrations (above 20%)
• Using glycerin without an occlusive layer to "seal in" the moisture
• Extremely dry climates (e.g. deserts, heated indoor spaces in winter)

The solution is simple: in dry climates, use glycerin at moderate concentrations and always "seal" it with an occlusive layer — a cream containing oils, petrolatum or a product with occlusive ingredients. This is the classic rule of hydration: humectant + occlusion.

Vegetable vs. synthetic glycerin

On the cosmetics market you'll often come across the term "vegetable glycerin". What does it mean?

Glycerin can come from two sources:

• Vegetable: obtained from plant oils (palm, coconut, rapeseed, soya) as a by-product of soap or biodiesel production
• Synthetic: produced from propylene (a petroleum derivative)

From a chemical standpoint, both forms are identical — they have the same molecular structure and the same effect on the skin. The only difference lies in the origin of the raw material.

Choosing vegetable glycerin can carry ethical and environmental significance. It's worth paying attention to the source — palm-oil glycerin is linked to deforestation, whereas rapeseed-oil glycerin has a smaller environmental footprint. Similar ethical dilemmas surround many cosmetic ingredients, which we explore in the context of making informed cosmetic choices.

Glycerin across different product types

Glycerin's versatility means you'll find it in almost every category of cosmetics:

• Serums and essences: as a primary moisturiser, often paired with hyaluronic acid
• Creams and lotions: hydration combined with occlusive ingredients
• Shampoos: hydrating the hair and scalp
• Makeup removers: soothing and hydrating during cleansing
• Lip balms: hydrating and protecting the lips

Summary

Glycerin is the gold standard among humectants — effective, safe, well-researched and widely available. Its only "flaw" is its lack of marketing glamour. In a world of cosmetics where novelty and exoticism sell, glycerin simply does its job quietly — and has done so for decades.

Don't be fooled by trendy ingredients that promise a revolution. Check whether your cosmetic contains a solid hydrating base — and verify it in our PurScore ingredient database. Sometimes the best solution is also the simplest.