Acid or Salt: How the Form Changes Both INCI and CAS

Somewhere on a supplier's spec sheet, "lactic acid" and "sodium lactate" get treated like they are basically the same thing with a slightly different name. On a Cosmetic Notification Form, they are not the same thing at all. Different INCI name, different CAS number, and in many cases a different job in the formula.

This trips people up more often with acids than almost any other ingredient category, because the acid form and the salt form of the same underlying molecule really are chemically related, just not identical, and cosmetic filings care about that distinction precisely.

Why the acid and the salt are declared separately

INCI, the International Nomenclature of Cosmetic Ingredients, is a standardized naming system built to identify exactly what is in a formula. Lactic acid and sodium lactate are related through neutralization chemistry (sodium lactate is what you get when lactic acid's acidic hydrogen is replaced with a sodium ion), but they behave differently on skin and in a formula. Lactic acid is acidic and functions as an exfoliant or pH adjuster. Sodium lactate is a humectant, pulling in moisture, and is much closer to pH-neutral.

Because they behave differently and have distinct chemical identities, they carry their own INCI names and their own CAS (Chemical Abstracts Service) numbers, the unique registry identifiers used to track specific substances.

Form	INCI name	Typical function	Chemical relationship
Acid	Lactic Acid	Exfoliant, pH adjuster	Parent acid
Sodium salt	Sodium Lactate	Humectant	Acid with hydrogen replaced by sodium

The same pattern shows up across a lot of acid-salt pairs used in cosmetics: glycolic acid versus its sodium salt, citric acid versus sodium citrate, salicylic acid versus sodium salicylate. Each pair is chemically related but declared and evaluated as distinct substances.

Why this matters for your Hotlist check and your filing

Canada's Cosmetic Ingredient Hotlist lists prohibited and restricted substances by specific identity, generally tied to INCI name and sometimes CAS number. If a formula genuinely contains sodium lactate as a humectant, but the filing lists it as lactic acid because someone assumed they were interchangeable, two problems follow. First, the Hotlist screening is being run against the wrong entry, since lactic acid's exfoliant-related conditions (concentration, free acid content, pH) do not apply the same way to sodium lactate. Second, the Cosmetic Notification Form itself becomes inaccurate, since it is supposed to reflect what is actually in the product.

A quick way to catch this before you file

• Pull the actual INCI name straight from your supplier's certificate of analysis or safety data sheet, not from a marketing name or a shorthand you have used internally
• If a raw material's technical name includes words like "sodium," "potassium," or "salt of," treat that as a signal to double check whether the acid or the salt form is what is actually in your formula
• Cross-reference the CAS number on your supplier documentation against the INCI name you are about to declare, since a mismatch there is often the first sign something has been mislabeled somewhere upstream
• Remember that some botanical extracts have no CAS number at all, which is a separate but related quirk of ingredient declaration, so absence of a CAS number is not automatically an error

The bigger habit this points to

Acid versus salt is one specific version of a broader pattern: trade names and shorthand descriptions do not belong on a filing, only INCI names do, and getting from a supplier's product name to the correct INCI declaration is a translation step that deserves actual attention, not an assumption based on how similar two names sound.

Cosmetic Comply's ingredient matching handles exactly this kind of translation, mapping supplier and trade names to the correct INCI name and CAS number, including catching acid-versus-salt mix-ups, before the formula goes to Hotlist screening and filing.