Lactic Acid

CAS Number:

50-21-5 (general CAS) . Other numbers exist for specific isomers: dl mixture (598-82-3), l-isomer (79-33-4), d-isomer (10326-41-7)

Chemical / IUPAC Name:

2-Hydroxypropanoic acid

INCI Name:

Lactic Acid

EC Number:

200-018-0

Molecular Formula:

C3H6O3

Molecular Weight:

90.08 g/mol

Other Names:

Milk acid, 2-Hydroxypropionic acid, E270

Uses:

Lactic acid is an organic compound belonging to the alpha-hydroxy acid (AHA) family . It is a multifunctional ingredient naturally found in the skin as part of the Natural Moisturizing Factor (NMF) . In its pure form, it is typically a colorless or yellowish, syrupy liquid . It is widely used across multiple industries for its exfoliating, moisturizing, and pH-adjusting properties.

· Cosmetics & Personal Care: The primary use is in skincare for its exfoliating and hydrating benefits. It is found in cleansers, serums, masks, peels, and moisturizers . It helps improve skin texture, reduce the appearance of fine lines and wrinkles, even out skin tone, and brighten a dull complexion .

· Pharmaceuticals: Used in topical creams and ointments . The lactate form is a key component in lactated Ringer's solution, an intravenous fluid used for fluid resuscitation . It is also an active ingredient in certain vaginal preparations (ATC code G01AD01) .

· Food Industry: Serves as a food additive (E270), functioning as a preservative, flavoring agent, and pH control agent in various products .

· Other Applications: Used in the textile industry for dyeing and printing, and in the production of biodegradable plastics .

Origin

Lactic acid is produced commercially via two main routes:

· Fermentation: By bacterial fermentation of carbohydrates such as glucose, sucrose, or lactose from sources like cornstarch, molasses, or beets . This method is the most common today .

· Chemical Synthesis: By a process involving the reaction of acetaldehyde with hydrogen cyanide to form lactonitrile, followed by hydrolysis to lactic acid .

What does Lactic Acid do in a formulation?

• Exfoliating Agent: Breaks down the bonds (desmosomes) that hold dead skin cells together on the surface, promoting their natural shedding and revealing fresher, brighter skin .
• Humectant / Moisturizing Agent: As a component of the skin's NMF, it attracts and retains moisture in the skin, helping to keep it hydrated .
• pH Adjuster: Used to lower and stabilize the pH of cosmetic and other formulations .
• Skin Conditioning Agent: Strengthens the skin's barrier by encouraging the production of ceramides . It also positively influences the skin's microbiome .
• Antimicrobial Agent / Preservative: Inhibits the growth of microorganisms in food and some cosmetic products .
• Chelating Agent: Can bind with metal ions, though this is a secondary function.

Safety Profile:

· General Hazard Classification: In its concentrated form, it is classified with GHS hazard statements H315 (Causes skin irritation) and H318 (Causes serious eye damage) .

· Concentration & pH Dependent Safety: Safety and irritation potential are highly dependent on concentration and pH. For cosmetic use:

  · Exfoliation: Typically used at concentrations 5-12% with a pH between 3 and 4 .

  · Leave-on Products: In some jurisdictions, leave-on products are restricted to concentrations lower than 3% to avoid contributing to pharmacological effects .

  · Professional Peels: Used at much higher concentrations (e.g., >30%) by trained professionals for deep chemical peels .

· Skin Sensitivity: It can cause mild irritation, especially at higher concentrations. Due to its larger molecular size, it is often considered gentler and better tolerated by sensitive or dry skin types than glycolic acid .

· Sun Sensitivity: As with all AHAs, its use can increase the skin's sensitivity to UV radiation. The use of sunscreen is recommended.

· Toxicity: Low acute toxicity. Recognized as safe (GRAS) for use in food .

· Regulatory Status: GRAS in the US . Approved as a food additive (E270) in the EU . Listed in major pharmacopoeias. Use in cosmetics is regulated regarding concentration and pH in many regions (e.g., Canada's Cosmetic Ingredient Hotlist) .

Technical profile: