Lactic Acid: What It Is and Why It's Used

Origin

Lactic acid was first isolated from sour milk by Carl Wilhelm Scheele in 1780 (the same chemist who isolated citric acid four years later). It occurs naturally as a product of lactose fermentation by lactic acid bacteria, and is a normal metabolite in human muscle tissue during anaerobic exercise. Industrial production is primarily through microbial fermentation of carbohydrates. It is one of the AHAs (alpha-hydroxy acids) and shares this classification with glycolic acid, citric acid, and others.

Why It's Used

In intimate hygiene products, lactic acid is used primarily as a pH adjuster — maintaining the vaginal pH range of approximately 3.8–4.5 that supports a healthy Lactobacillus-dominant microbiome and resists pathogen overgrowth. It also appears in the skin's own natural moisturising factor. As an AHA, it exfoliates by loosening bonds between dead skin cells, but this is not the primary function in intimate hygiene applications. The claim space around intimate hygiene products is specifically regulated: these products are regulated as cosmetics, not as treatments for medical conditions.

Elsewhere

Lactic acid is widely used as a food additive and preservative (E270), in the production of polylactic acid (PLA) bioplastics, in pharmaceutical preparations, and in industrial processes including leather tanning and textile production.

What the Framework Sees

a labelling rule genuinely unlike anything else in this series.

Get the full analysis in Volume Six →