Alpha Hydroxy Acids and the Hotlist pH and Limit Rules

Alpha hydroxy acids are a good example of why the Cosmetic Ingredient Hotlist is not a simple yes-or-no list. Glycolic acid and lactic acid are not banned. They are also not unrestricted. They sit in that middle category where the Hotlist attaches conditions, and getting those conditions wrong is one of the more common reasons a small brand's exfoliating toner or peel pad gets flagged during review.

Why AHAs get conditional treatment instead of a flat rule

AHAs work by loosening the bonds between skin cells at the surface, which is genuinely useful for texture and tone, but that same mechanism is what makes concentration and formulation conditions matter. A glycolic acid toner at a low, well-buffered concentration behaves very differently on skin than a highly concentrated, low-pH peel product. The Hotlist's role is to draw a line around what is reasonable for a cosmetic to do without crossing into territory that needs professional application or drug-level oversight.

What actually gets checked

When an AHA-containing formula gets evaluated against the Hotlist, the things that matter are:

• Total AHA concentration. The percentage of glycolic acid, lactic acid, or other AHA present in the finished formula.
• Free acid content. This is the detail people skip. A formula's pH determines how much of the total acid is in its active, unbuffered form versus buffered or neutralized. Two products with identical raw glycolic acid percentages can have very different free acid levels depending on how much of the acid was neutralized during formulation. The Hotlist's conditions are tied to what is actually active, not just what was weighed out on the bench.
• Finished product pH. Directly tied to free acid content, and typically has to fall within a defined range for cosmetic use.
• Required labeling. AHA products generally need to carry a sun-sensitivity warning, since increased photosensitivity is a well-documented effect of AHA use, independent of concentration within the cosmetic range.

Practical formulating notes

If you are building an AHA product for the Canadian market, a few habits keep you out of trouble:

• Measure and record your finished product's pH at the batch level, not just the theoretical pH from your formulation software
• Have your free acid content verified rather than assumed, especially if you are neutralizing part of the acid with a base to soften the formula
• Build the sun-sensitivity warning into your label template from the start, rather than treating it as an afterthought added right before filing
• Recheck the Hotlist entry directly before filing, since concentration limits and conditions are the kind of detail that can be updated, and a general guide like this one should not be treated as a substitute for the current Hotlist text

A simplified illustration

Ingredient	INCI name	Common use level	Key condition
Glycolic acid	Glycolic Acid	Varies by product type	Free acid content and finished pH within Hotlist condition; sun-sensitivity warning
Lactic acid	Lactic Acid	Varies by product type	Same category of condition as glycolic acid
Sodium lactate (buffered salt form)	Sodium Lactate	Often used as humectant, not primary exfoliant	Distinct INCI and CAS from lactic acid itself, generally not subject to the same exfoliant-specific conditions

That last row is worth sitting with for a second. Lactic acid and its salt form, sodium lactate, are chemically related but are declared under separate INCI names with separate CAS numbers, and they behave very differently in a formula. Swapping one for the other in your ingredient deck without checking which one you actually used is a real, recurring filing error.

Why this is worth double-checking before filing, not after

An AHA product notified with the wrong free acid assumption, or missing the sun-sensitivity warning on the label, is the kind of thing that surfaces during review rather than at launch, which means a delay right when you wanted the product live. Getting the pH and free acid numbers verified before the Cosmetic Notification Form goes in saves that back-and-forth.

Cosmetic Comply checks AHA and other Hotlist-restricted ingredients against current concentration and condition rules as part of matching your formula to INCI and CAS, with a compliance reviewer confirming the result before the notification is filed.