Sodium Lactate

Overview

Sodium lactate is the sodium salt of lactic acid. It is produced by fermentation of carbohydrates (typically corn or beet sugar) into lactic acid, which is then neutralized with sodium hydroxide. The cosmetic grade is supplied as a 60% or 90% liquid solution — viscous, clear, and almost odourless.

It is one of the most useful “all-rounder” humectants in cosmetic formulation. Sodium lactate is a natural moisturizing factor — meaning the skin produces it itself as part of the natural skin chemistry that binds water in the upper layers. Topical sodium lactate integrates naturally with this skin chemistry and provides effective, gentle hydration.

Shelf life as a liquid solution is 2-3 years stored cool and dark.

In cold-process soap, sodium lactate plays a different role: it hardens the finished bar, speeds up unmolding, and improves the smooth surface of the bar.

What it does in a formula

As a humectant, sodium lactate binds water to the upper skin layers at use rates of 1-5%. It is gentler than glycerin and significantly less tacky — many formulators prefer sodium lactate over glycerin in oily or combination skin formulas because of the lighter feel.

Sodium lactate also has a small natural moisturizing factor effect — it integrates with the skin’s own hydration chemistry and provides longer-lasting hydration than passive humectants alone.

In cold-process soap, the sodium ion contributes to the soap’s hardness, allowing earlier unmolding and a firmer final bar. The lactate portion does not significantly affect the soap chemistry.

It also acts as a mild pH buffer in formulas at slightly acidic pH.

How to use

For skincare: add to the water phase. Tolerates heat-and-hold to 80 C without issue.

For soap: dissolve in the lye solution (or add at trace) at 1-3% of total oils.

Usage rates by product type (60% sodium lactate solution):

• Face creams (humectant): 1-3%
• Body lotions: 2-5%
• Hand creams: 2-5%
• Toners (hydrating): 1-3%
• Cold-process soap (hardness): 1-3% (of oil weight)
• Foot creams: 2-5%
• Hair leave-ins: 1-3%

Best for / Worst for

Best for: light hydrating face creams, lotions for oily/combination skin (less tacky than glycerin), cold-process soap (firms the bar), foot creams (mild keratolytic action helps with calluses), natural moisturizing factor positioning.

Worst for: very dry skin needing heavy occlusion (sodium lactate is light), oil-only formulas (water-soluble), formulas where you want a strong active rather than gentle humectant support.

Common pitfalls

Photosensitivity warning. Sodium lactate at 5%+ in leave-on products can slightly increase sun sensitivity, similar to other AHA-related ingredients. For high-percentage formulas, suggest SPF use.

Strength confusion. Sodium lactate is supplied as 60% or 90% solutions. A 90% solution is 50% more concentrated than a 60% solution at the same use rate. Read the supplier specification.

Mistaking it for lactic acid. Sodium lactate is the salt (pH near neutral); lactic acid is the acid (pH near 2). They behave very differently in formulas. Sodium lactate is a humectant; lactic acid is an exfoliating AHA.

Substitutes

• Sodium PCA — different chemistry, similar light humectant role.
• Glycerin — heavier, stickier, more common.
• Propanediol — different chemistry, light humectant.
• Lactic acid (low percentage with sodium hydroxide neutralization) — creates sodium lactate in situ.