Lactic acid
Lactic acid is an alpha hydroxy acid (AHA) derived from milk, fruits, and vegetables, widely used in skincare for its gentle exfoliating, hydrating, and brightening properties. As a water-soluble acid, it works by breaking down the bonds between dead skin cells, allowing them to shed more easily and revealing smoother, more radiant skin underneath. Unlike some other AHAs, lactic acid is known for its humectant properties, meaning it attracts and retains moisture, making it an excellent choice for individuals with dry or sensitive skin.
One of lactic acid’s biggest benefits is its ability to improve skin texture and tone while minimizing the appearance of fine lines, dullness, and hyperpigmentation. It stimulates cell turnover and collagen production, which helps promote firmer, plumper skin over time. This makes it a popular ingredient in anti-aging treatments, chemical peels, and brightening serums. Because lactic acid molecules are larger than those of glycolic acid, they penetrate the skin more slowly, making it a milder and less irritating option for exfoliation.
Lactic acid is often used in concentrations ranging from 5% to 10% in over-the-counter products, such as cleansers, toners, masks, and serums. Higher concentrations, typically above 10%, are found in professional-grade chemical peels. Regular use can help fade sun spots, post-inflammatory hyperpigmentation (PIH), and melasma, making it a go-to ingredient for those dealing with uneven skin tone.
Despite its gentle nature, lactic acid can increase sun sensitivity, so using sunscreen daily is essential when incorporating it into a skincare routine. It pairs well with hydrating ingredients like hyaluronic acid and soothing agents like niacinamide to counteract any potential irritation. Whether used as a mild daily exfoliant or in a stronger treatment, lactic acid is a highly effective ingredient for achieving softer, smoother, and more radiant skin.
Lactic acid is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate (or the lactate anion). The name of the derived acyl group is lactoyl.
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| Names | |||
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| Preferred IUPAC name
2-Hydroxypropanoic acid | |||
Other names
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| Identifiers | |||
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3D model (JSmol)
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| 1720251 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.000.017 | ||
| EC Number |
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| E number | E270 (preservatives) | ||
| 362717 | |||
| KEGG | |||
PubChem CID
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| RTECS number |
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| UNII |
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| UN number | 3265 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| C3H6O3 | |||
| Molar mass | 90.078 g·mol−1 | ||
| Melting point | 18 °C (64 °F; 291 K) | ||
| Boiling point | 122 °C (252 °F; 395 K) at 15 mmHg | ||
| Miscible | |||
| Acidity (pKa) | 3.86, 15.1 | ||
| Thermochemistry | |||
Std enthalpy of
combustion (ΔcH⦵298) |
1361.9 kJ/mol, 325.5 kcal/mol, 15.1 kJ/g, 3.61 kcal/g | ||
| Related compounds | |||
Other anions
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Lactate | ||
Related carboxylic acids
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Related compounds
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| Pharmacology | |||
| G01AD01 (WHO) QP53AG02 (WHO) | |||
| Hazards | |||
| GHS labelling: | |||
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| H315, H318 | |||
| P280, P305+P351+P338 | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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In solution, it can ionize by a loss of a proton to produce the lactate ion CH
3CH(OH)CO−
2. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.
Lactic acid is chiral, consisting of two enantiomers. One is known as L-lactic acid, (S)-lactic acid, or (+)-lactic acid, and the other, its mirror image, is D-lactic acid, (R)-lactic acid, or (−)-lactic acid. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid. Lactic acid is hygroscopic. DL-Lactic acid is miscible with water and with ethanol above its melting point, which is about 16 to 18 °C (61 to 64 °F). D-Lactic acid and L-lactic acid have a higher melting point. Lactic acid produced by fermentation of milk is often racemic, although certain species of bacteria produce solely D-lactic acid. On the other hand, lactic acid produced by fermentation in animal muscles has the (L) enantiomer and is sometimes called "sarcolactic" acid, from the Greek sarx, meaning "flesh".
In animals, L-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. The concentration of blood lactate is usually 1–2 mM at rest, but can rise to over 20 mM during intense exertion and as high as 25 mM afterward. In addition to other biological roles, L-lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), which is a Gi/o-coupled G protein-coupled receptor (GPCR).
In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as cavities. In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution. These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.
Lactic acid is produced in human tissues when the demand for oxygen is limited by the supply. This occurs during tissue ischemia when the flow of blood is limited as in sepsis or hemorrhagic shock. It may also occur when demand for oxygen is high such as with intense exercise. The process of lactic acidosis produces lactic acid which results in an oxygen debt which can be resolved or repaid when tissue oxygenation improves.
