Glycerine, Propylene Glycol & EDTA

These three ingredients rarely get marketed on a product’s front label, but pull any well-formulated lotion, serum or cleanser apart and you’ll find at least one of them doing quiet, essential work in the background.

Vegetable Glycerine: the humectant everyone uses

Vegetable Glycerine USP is one of the most widely used humectants in cosmetic chemistry — it draws moisture from the air into the skin, and appears in nearly every formulation category, from cleansers to heavy creams. If you’re formulating your first product and want one reliable moisture-supporting ingredient to include, glycerine is very likely it.

Propylene Glycol: humectant and solvent, doing double duty

Propylene Glycol works similarly to glycerine as a humectant, but it also functions as a solvent — helping preservatives and active ingredients dissolve and disperse evenly through a formulation rather than clumping or settling unevenly. That dual role is why it turns up specifically in formulas with actives or preservative systems that need help distributing properly.

EDTA Disodium: the ingredient that protects everything else

EDTA Disodium does a completely different job — it’s a chelating agent, binding trace metal ions that would otherwise be present in your water phase or raw materials. Those trace metals can reduce preservative efficacy and destabilise a formula over time. Adding EDTA isn’t about a direct skin benefit; it’s about protecting the stability and preservation of everything else in the formula.

Do you need all three?

Not necessarily in every formula, but a strong default: glycerine as a humectant in nearly anything water-based, propylene glycol when you’re dispersing actives or a preservative system that benefits from it, and EDTA whenever product stability and preservative performance matter — which, for anything sold with a real shelf life, is essentially always.

See our guide to choosing a preservative for how EDTA and propylene glycol support a preservative system’s real-world performance.