Lactic Acid: Uses, Strength and Safety Guide

Lactic acid is the acid that forms when milk sours and when sugars ferment. Commercial lactic acid is made by fermenting sugars or starch and is usually sold as a concentrated water solution, often around 80–90%, rather than as pure acid.

• Formula: C3H6O3 (2-hydroxypropanoic acid)
• CAS number: 50-21-5 (L-form: 79-33-4)
• Molar mass: about 90.1 g/mol
• Appearance: clear, colourless to pale yellow, syrupy liquid with a mild sour smell
• Solubility: mixes completely with water

It's an alpha hydroxy acid (AHA), the same family as glycolic acid, but with a larger molecule, which is why it's often described as milder.

Azlok lists Lactic Acid in its cosmetic raw ingredients range, for creams, cleansers, toners and other personal care products. The product name doesn't state the strength or pack size, so check the listing or ask for the specification before you build a formula around it.

For the current rate, see today's price per kg.

• Cosmetics: a pH adjuster in creams, lotions and cleansers; a humectant that helps hold moisture; and an exfoliant in products aimed at rough or dull-looking skin.
• Hair care: lowering pH in shampoos and conditioners.
• Soap making: small amounts are added to some bar soap recipes to make a harder bar.
• Industry: leather tanning and deliming, textile finishing, descaling, and as the raw material for PLA (polylactic acid) plastic.
• Food: an acidulant, but only food-grade lactic acid under FSSAI rules. This listing isn't sold as food grade.

Lactic acid is strong in concentrated form, so always dilute it into the water phase, never the other way round.

1. Check the strength: work out how much actual acid is in your bottle. With an 80% solution, 10 g gives 8 g of lactic acid.
2. pH adjustment: make a 10% dilution in distilled water and add it drop by drop to the finished, cooled product, checking pH with a meter or strips after each addition.
3. Exfoliating products: US cosmetic safety reviewers (CIR) have judged AHAs safe in consumer products at up to 10% with a final pH of 3.5 or higher. Treat that as an upper limit, not a target; many makers use far less.
4. Patch test: AHA products can sting and make skin more sensitive to the sun, so patch test and advise daily sunscreen use.
5. Preserve: water-based products still need a preservative system that works at your final pH.

• Concentrated lactic acid can cause serious eye damage and skin irritation. Wear gloves and safety glasses.
• If it splashes in the eyes, rinse with plenty of water for at least 15 minutes and get medical help.
• Keep it away from strong alkalis and strong oxidisers. It reacts with bases, giving off heat.
• Store in a tightly closed plastic or glass bottle in a cool place. It can corrode some metals.
• Keep it away from children and away from food.
• Dilute small amounts with plenty of water before disposal, as local rules allow.

• Formulators: confirm the strength (for example 80% or 88%) and source before scaling a recipe, since the active amount changes with it.
• Small makers: a small bottle lasts a long time when it's used only for pH adjustment.
• Food use: buy a certified food-grade product within FSSAI rules, not this cosmetic listing.
• Production: for 25 kg or more, send a bulk inquiry.

If you sell finished cosmetics in India, keep supplier documents ready, as products must meet BIS and CDSCO rules.