The Thirsty Ingredients: Five Humectants That Keep Skin Hydrated

If an emulsifier is a diplomat, a humectant is a magnet for water. These are the ingredients that attract moisture — from your formula, from the deeper layers of skin, and from the air itself — and hold it where you want it: at the surface, keeping skin plump, soft, and comfortable.

They're some of the most satisfying ingredients to work with, because the results are immediate and tactile. But humectants carry a quiet catch that every formulator should understand: in the wrong conditions, a humectant can pull water out of the skin rather than into it. More on that below.

Here are five worth knowing, and how to use them well.

1. Glycerin (Glycerol)

INCI: Glycerin

Type: Humectant · Typical use: 2–10% (most commonly 3–5% in leave-on products) · ✅ COSMOS-approved (vegetable-derived grades)

The undisputed workhorse. Affordable, exceptionally well-studied, and suitable for almost every product type. Vegetable glycerin is a by-product of soap and biodiesel manufacture, making it widely available with good sustainability credentials. It genuinely supports the skin barrier over time, not just surface feel.

• Loves: the water phase of almost anything — creams, lotions, toners, serums, cleansers, and rinse-off products.
• Watch: above approximately 5–10%, glycerin can feel sticky and tacky in leave-on products, particularly in low-humidity conditions. Pair with a good emollient and consider a complementary humectant such as betaine to soften the tack. Very high levels can also feel occlusive and heavy on the skin.

2. Sodium Hyaluronate (Hyaluronic Acid)

INCI: Sodium Hyaluronate

Type: Humectant · Typical use: 0.1–2% (potent — a little goes a long way) · ✅ COSMOS-approved (biotech-fermented grades widely accepted — always verify with your supplier and certifier)

The celebrity humectant. Sodium hyaluronate — the more stable, water-soluble salt form used in formulation, as distinct from the free acid — can hold many times its own weight in water, giving an immediate plumping, bouncy hydration feel. Molecular weight matters: high molecular weight (HMW) grades form a hydrating film at the skin surface; low molecular weight (LMW) grades are marketed for deeper skin penetration. Many premium serums blend two or more molecular weight grades for a layered effect.

• Loves: serums, essences, gel-creams, and hydrating mists. Disperse the powder in cold or room-temperature water and allow it to fully hydrate into a gel before incorporating into the formula — do not add to hot water as this can degrade the polymer.
• Watch: in very dry ambient air, the surface film can feel tight as it desiccates — always partner with glycerin and an occlusive or emollient to seal in the moisture attracted. Use levels are very low; over-dosing wastes a costly ingredient and can produce a sticky or pill-prone skin feel.

3. Sodium PCA

INCI: Sodium PCA

Type: Humectant · Typical use: 0.5–2.5% · ✅ COSMOS-approved (verify grade and supplier)

A component of the skin's own Natural Moisturising Factor (NMF) — the complex blend of humectants the skin produces for itself. Because it is skin-identical, sodium PCA is beautifully lightweight and non-sticky, making it a favourite for facial serums and toners where glycerin's tack would be unwelcome. It is the sodium salt of pyrrolidone carboxylic acid, produced naturally in the skin from the breakdown of filaggrin.

• Loves: light serums, toners, and weightless hydrating gels; any application where you want meaningful hydration without heaviness or residue.
• Watch: highly hygroscopic in its raw powder form — store tightly sealed in a cool, dry environment. Generally very well tolerated across skin types.

4. Betaine (Trimethylglycine)

INCI: Betaine

Type: Humectant · Typical use: 0.5–5% · ✅ COSMOS-approved (sugar-beet-derived)

A gentle, plant-derived humectant (most commonly sourced from sugar beet molasses) that also functions as an osmolyte, helping cells manage osmotic water balance under stress. It is soothing, non-tacky, and an excellent partner to glycerin — it can meaningfully reduce glycerin's stickiness whilst maintaining or enhancing overall hydration performance.

• Loves: creams, cleansers (it helps soften the harshness of surfactant systems), and glycerin-reduction blends where you want hydration without tack. A good option for sensitive and reactive skin formulations.
• Watch: supplied as a solid or concentrated solution depending on the grade — ensure it is fully dissolved into the water phase before proceeding. Very few formulation downsides, which is a large part of its appeal.

5. Panthenol (Provitamin B5)

INCI: Panthenol

Type: Humectant + skin conditioner · Typical use: 0.5–5% · ✅ COSMOS-approved (verify — some grades are nature-identical synthetic; confirm with your supplier)

A dual-action ingredient: it functions as a humectant and also soothes, supports skin barrier repair, and improves the sensory feel of a formula. Once absorbed, panthenol is converted to pantothenic acid (vitamin B5) in the skin. Available as a viscous liquid (D-panthenol, the biologically active enantiomer) or as a powder. Widely used in barrier-repair, after-sun, and scalp-care positioning.

• Loves: soothing creams, after-sun products, hair conditioners and masks, barrier serums, and baby formulations.
• Watch: most stable at a mildly acidic to neutral pH (approximately 4.0–7.0); can hydrolyse slowly at extreme pH values over time. Always confirm the COSMOS status of your specific grade with your supplier — nature-identical (synthetic) panthenol is not COSMOS-approved, whereas naturally derived or biotechnology-derived grades may be, subject to documentation.

Honourable mentions

• Propanediol (INCI: Propanediol; typically 1,3-propanediol, corn-derived) — a humectant and a solvent that can enhance preservative efficacy and help dissolve challenging actives and fragrances. A well-regarded greener alternative to propylene glycol. ✅ COSMOS-approved (verify grade).
• Sodium Lactate (INCI: Sodium Lactate) — an NMF component and effective humectant, but note that it is the sodium salt of lactic acid (a mild AHA), so consider the overall acid load and pH of your formula carefully. At higher levels it may increase photosensitivity — flag this in your safety assessment. ✅ COSMOS-approved (verify grade).
• Honey, aloe vera juice, and hydrolysed proteins — these naturally humectant-rich materials each bring their own compelling marketing narrative and additional skin-benefit claims. Bear in mind they introduce additional considerations around microbial control, batch-to-batch standardisation, and allergen declaration.

A few honest formulating truths

• The humidity paradox is real. Humectants attract water from wherever there is most of it. In humid air, that is the atmosphere — ideal. In very dry conditions (below approximately 40–50% relative humidity), a humectant with insufficient occlusion to back it up can draw water up from the deeper layers of skin and allow it to evaporate, leaving the skin feeling tighter than before. The answer is almost always to pair humectants with an occlusive and/or emollient that retains the moisture attracted. This is why simply increasing glycerin is rarely the complete solution to a dryness complaint.
• Layer your hydration. The most elegant approach uses a complementary team: a fast-acting humectant (glycerin), a film-former (sodium hyaluronate), a skin-identical component (sodium PCA or betaine), and an occlusive layer to seal it in place.
• More is not better. Beyond a certain threshold, humectants stop adding measurable hydration and begin contributing tack, weight, or an unpleasant grabby skin feel. Always formulate to the lowest effective level and validate with consumer or panel testing.
• Mind the water phase and pH. Most humectants are added to the water phase. Some — including panthenol and sodium lactate — are pH-sensitive or will shift the pH of your formula, so always check and adjust your finished pH after all additions are complete.
• Hydration is not the same as moisturisation. Humectants contribute water; they cannot replace the lipids that a compromised skin barrier needs. A truly effective moisturiser typically requires both humectants and emollients/occlusives working together.

Quick reference

*Verify COSMOS status for the specific grade and supplier — some grades are biotech-fermented or nature-identical and require confirmation against the latest permitted ingredients list and your certifier's guidance.

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This article is educational and is not a substitute for the manufacturer's technical data sheet, your own stability and safety testing, or a qualified cosmetic safety assessor's review. Always verify use levels, processing conditions, and regulatory or certification status against the supplier's current documentation and the applicable regulations for your target market.