How is lactic acid formed

Lactic acidAcidsLactic acid is an organic hydroxycarboxylic acid that is produced as a metabolic intermediate and during bacterial lactic acid fermentation. It has caustic, acidic and antiseptic properties and is used, among other things, for warts, corns, to strengthen the vaginal environment, as a pharmaceutical excipient and for the production of active ingredient salts. It is also of great importance in the production of food, for example sour milk products and cheese. Concentrated lactic acid can cause skin irritation and serious eye damage if used improperly.

synonymous: Acidum lacticumPhEur, Lactic acid, E 270, 2-hydroxypropionic acid, 2-hydroxypropionic acid


Lactic acid is available as a pure substance in pharmacies and drug stores. It is contained in medicines, cosmetics and medical products, including wart remedies, corns, vaginal care products, skin care products and callus removal products.

Structure and properties

The lactic acid (C.3H6O3, Mr = 90.1 g / mol) is an organic acid that belongs to the α-hydroxycarboxylic acids. It is available as a colorless to pale yellow, syrupy liquid with a typical odor and is miscible with water. In addition to lactic acid, the liquid can also contain condensation products (esters) and water according to the pharmacopoeia. Lactic acid is a racemate that results from the S.- and R.-Enantiomer consists. The S.-Enantiomer corresponds to L - (+) - lactic acid and is physiological for humans. The R.-Enantiomer is also known as D - (-) - lactic acid.

Lactic acid was first isolated from sour milk in the 18th century. It is obtained through bacterial fermentation from sugars such as glucose and lactose, for example with the help of lactobacilli and certain streptococci. One speaks of lactic acid fermentation. The salts and esters of lactic acid are known as lactates or lactates. The pKa (carboxylic acid) is 3.86.

Lactic acid occurs in higher concentrations in various foods, for example in yoghurt, sauerkraut, sour bread, quark, cheese, in sour milk and in some beverages (e.g. Rivella®).


The lactic acid (ATC G01AD01) has corrosive, acidic, keratolytic and antiseptic properties depending on the concentration of the product. In the vagina, it is involved in maintaining the acidic environment and in the immune system. It also plays an important role in the metabolism as a metabolite of pyruvate, for example in the muscles.

Fermentation of glucose to lactic acid in lactobacilli, click to enlarge. Illustration © PharmaWiki

application areas

In the form of suitable preparations:

unwanted effects

Concentrated (pure) lactic acid is corrosive and, if used improperly, can cause skin irritation and serious eye damage. The corresponding precautionary measures in the safety data sheet must be observed.

see also

Acids, lactobacilli

  • Agroscope
  • Pharmaceutical product information (CH)
  • European Pharmacopoeia PhEur
  • Chemistry textbooks
  • Encyclopedias of food technology
  • Safety data sheet

Conflicts of Interest: None / Independent. The author has no relationships with the manufacturers and is not involved in the sale of the products mentioned.

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This article was last changed on 11/10/2020.
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