Skin that is short on water feels tight, looks dull and flakes, and oil on its own cannot put that water back. Glycerin can. It is in almost every moisturizer you have used, and it is one of the most studied ingredients in skincare.

The short answer

Glycerin is a humectant, which means it attracts water and holds on to it. Applied topically, it pulls water into the outer layer of your skin, helps a damaged barrier recover faster, and helps old surface cells shed evenly instead of building up into rough patches. Skin feels softer the same day. It suits every skin type and works best inside a moisturizer that also contains oils and fats.

Diagram of the outer skin layer as a wall of cells, with glycerin molecules holding water droplets and a channel carrying glycerin upward.
Your skin makes its own glycerin and carries it upward through channels. Applied topically, glycerin binds water in the outer layer.

What it does

Glycerin is a humectant, which means it attracts water and holds on to it. Applied topically, it pulls water into the outer layer of your skin, helps a damaged barrier recover faster, and helps old surface cells shed evenly instead of building up into rough patches. Skin feels softer the same day. It suits every skin type and works best inside a moisturizer that also contains oils and fats.

Why skin runs short on water

Most people assume the top layers of skin are dead and irrelevant. The outermost layer actually signals to the deeper layers to regulate hydration, collagen and cell renewal, and it decides how much water your skin keeps.

Two things hold water in that layer: water-attracting substances inside your cells, including glycerin your skin makes itself, and a thin layer of oils and fats on the surface that helps stop water from evaporating. When either runs low, water leaves faster than it is replaced, and skin feels tight and starts to flake.

Dry and dehydrated skin are not an either/or. Dehydrated skin is short on water. Dry skin makes too little oil, and without enough oils and fats it struggles to hold water too.

Humectants, emollients and occlusives

Moisturizers work through three kinds of ingredients. Humectants attract water and hold it, as glycerin, hyaluronic acid and panthenol do. Emollients are oils and fats that fill the gaps between your surface cells, which makes skin feel soft and smooth, as squalane and ceramides do. Occlusives, such as petrolatum, form a thin film over the surface that slows evaporation.

A humectant brings water in. Without oils and fats over it, more of that water can evaporate again, which is why glycerin is almost always formulated alongside emollients and occlusives.

How glycerin works

Glycerin is a very small molecule that moves into the outer layer of your skin and binds water there. Your oil glands break down fats into glycerin, and channels in your skin cells called aquaporin-3 carry glycerin and water through the upper layers. In mice that lacked those channels, skin held about half as much water and repaired its barrier more slowly, and glycerin applied topically corrected both.

Beyond holding water, glycerin helps a damaged barrier recover faster. It helps the natural enzymes that loosen old surface cells do their work, which means cells shed evenly instead of piling up into rough texture. In dry conditions it also keeps the fats between your surface cells flexible, where they would otherwise stiffen and let water escape.

The result is skin that feels softer, looks smoother and copes better with the rest of your routine, because an intact barrier keeps irritants out as well as water in.

Where glycerin comes from

Glycerin is part of the structure of every fat and oil, from plants and from animals. When those fats are split apart, during soap making or biodiesel production, glycerin is released and then purified. It can also be made in a lab from starting materials derived from propylene.

The source does not change the molecule. Purified glycerin from a plant oil, an animal fat or a lab is the same substance, and the US Cosmetic Ingredient Review panel has assessed it as safe as used in cosmetics. Plant-derived on a label describes sourcing, not how glycerin works on your skin.

Two panels: water drawn into skin cells escapes upward without a surface layer, and stays inside when a layer of oils and fats covers it.
Glycerin brings water in. A layer of oils and fats on the surface keeps more of it from evaporating, which is why the two belong together.

What the research shows

Glycerin has decades of research behind it, gathered in a 2008 review in the British Journal of Dermatology. In a placebo-controlled, double-blind trial in people with atopic eczema, a 20 percent glycerin cream raised skin hydration within one week compared with the same cream without glycerin, and hydration stayed higher for two weeks after people stopped. A larger trial of 197 people found the same strength well tolerated over a month, and dryness improved in every group, including the cream without glycerin, which shows the whole moisturizer matters.

In healthy volunteers, skin with glycerin recovered faster after researchers disrupted a small patch of the barrier on purpose. The aquaporin-3 work comes from mice, and early findings on wound healing still need confirming in people.

What to look for on a label

More glycerin helps, up to a point

The amount of glycerin changes how much it hydrates. In studies, raising it from 5 to 10 percent improved hydration, and on very dry lower legs the benefit peaked at around 20 to 40 percent. At higher levels glycerin can feel sticky, which is why a face product balances hydration against how it feels.

Brands rarely print the percentage. Ingredient lists run from the largest amount to the smallest, which means glycerin near the top is there in a good amount. Glycerin, glycerol and glycerine are the same ingredient. Glyceryl stearate is a different substance made from glycerin, with a different job.

Where it sits in your routine

Most glycerin comes in a moisturizer, which means it goes on at your moisturizer step. If yours is in a serum or a toner, apply it after cleansing and follow with a moisturizer that contains oils and fats.

What works best with glycerin

Glycerin does not interact with other ingredients, which is why it works alongside everything in your routine. It pairs well with ceramides, cholesterol and fatty acids, the three main fats that hold your barrier together, because they rebuild the gaps between your surface cells while glycerin brings water in. Sunscreen every morning, reapplied through the day, protects that barrier.

Common questions

Does glycerin pull water out of my skin in dry air?

Not when it is in a well-made moisturizer. Glycerin attracts water from wherever there is more of it. In very dry air, pure, undiluted glycerin can draw water out of the outer layer of your skin.

In a moisturizer, glycerin is diluted and formulated with oils and fats that slow evaporation, which keeps the water where your skin needs it. In dry conditions it also keeps your skin's surface fats flexible, which helps your barrier hold water in a separate way.

Glycerin or hyaluronic acid?

Both, and many moisturizers use the two together. Glycerin is a very small molecule your skin also makes itself, with research behind it for barrier recovery as well as hydration. Hyaluronic acid holds water at the surface and gives skin a plumper look. Both are excellent at what they do.

How soon will I see something?

Your skin feels softer the same day, and in the eczema trial hydration measured higher within one week. Give it about four weeks of daily use for dryness and roughness to settle, and photograph your skin on day one, in the same spot in natural daylight, to compare.

Is it safe in pregnancy?

Yes. Glycerin is generally considered safe, and it is a substance your own body makes. Skincare ingredients are almost never tested on pregnant people, which is why we suggest checking with your OB or midwife before starting anything new.

A plant sprig with an oil droplet and a lab flask, each with an arrow pointing to one clear droplet containing a molecule outline.
Whether it starts as a plant oil or in a lab, purified glycerin is the same substance and works the same way on your skin.

How to use it

  • Use a glycerin moisturizer morning and night. There is nothing to build your tolerance up to with glycerin.
  • If your glycerin is in a serum or a toner, follow it with a moisturizer that contains oils and fats.
  • In winter, or anywhere with indoor heating, move to a richer moisturizer rather than adding more products.
  • If your skin is eczema-prone, moisturize every day, including when your skin looks clear. Scratching weakens the barrier, and daily moisturizing strengthens it between flares.
  • Broad spectrum SPF 30 or higher every morning, reapplied through the day.
Evidence and sources
  • Fluhr JW, Darlenski R, Surber C. Glycerol and the skin: holistic approach to its origin and functions. British Journal of Dermatology, 2008;159(1):23-34. The review covering hydration, barrier recovery, shedding, the aquaporin-3 pathway, the lipid phase work in dry conditions, the concentration studies and the effect of undiluted glycerol. Read the review
  • Breternitz M, Kowatzki D, Langenauer M, Elsner P, Fluhr JW. Placebo-controlled, double-blind, randomized, prospective study of a glycerol-based emollient on eczematous skin in atopic dermatitis: biophysical and clinical evaluation. Skin Pharmacology and Physiology, 2008;21(1):39-45. The eczema trial of a 20 percent glycerin cream described here. Read the study
  • LodΓ©n M, Andersson AC, Anderson C, et al. A double-blind study comparing the effect of glycerin and urea on dry, eczematous skin in atopic patients. Acta Dermato-Venereologica, 2002;82(1):45-47. The 197-person trial. Read the study
  • Fluhr JW, Gloor M, Lehmann L, Lazzerini S, Distante F, Berardesca E. Glycerol accelerates recovery of barrier function in vivo. Acta Dermato-Venereologica, 1999;79(6):418-421. The barrier recovery study in volunteers. Read the study
  • Hara M, Verkman AS. Glycerol replacement corrects defective skin hydration, elasticity, and barrier function in aquaporin-3-deficient mice. Proceedings of the National Academy of Sciences, 2003;100(12):7360-7365. The aquaporin-3 mouse research. Read the study
  • LodΓ©n M. Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders. American Journal of Clinical Dermatology, 2003;4(11):771-788. Background on how humectants and fats work together in a moisturizer.
  • Becker LC, Bergfeld WF, Belsito DV, et al. Safety assessment of glycerin as used in cosmetics. International Journal of Toxicology, 2019;38(3 suppl):6S-22S. The Cosmetic Ingredient Review safety assessment, including how glycerin is produced. Read the assessment
  • Tan HW, Abdul Aziz AR, Aroua MK. Glycerol production and its applications as a raw material: a review. Renewable and Sustainable Energy Reviews, 2013;27:118-127. How glycerin is released during soap and biodiesel production. Read the review

A note on the evidence. Glycerin's effect on hydration and barrier recovery has been measured in people, including placebo-controlled trials in eczema-prone skin, though those trials are small to moderate in size and used a 20 percent cream. The aquaporin-3 findings come from mice and the work on skin fats in dry conditions from laboratory models, which is why we describe those as how glycerin is understood to work.

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