Glycolic acid is a low-molecular-weight, two-carbon α-hydroxy acid organic chemical compound with alcohol and acid groups.

α-Hydroxy acids include glycolic acid, lactic acid, tartaric acid, malic acid, citric acid, all of which are present in many foods and milk sugars.

It occurs as a fine white powder or colourless liquid soluble in water, organic solvents such as methanol, ethanol, ethyl acetate, slightly soluble in diethyl ether, insoluble in hydrocarbons.

It is produced naturally from 

• fruit juices and sugar cane
• certain iron-sulphur-oxidant chemolithotrophic bacteria
• yeasts and acetic acid bacteria from ethylene glycol
• cell catalysis Gluconobacter oxydans
• glyconlonistitrile by hydrolysis with nitrilase enzyme activity of Alcaligenes sp

It is produced industrially by chemical synthesis from

• synthesis gas treated with carbon monoxide and water from formaldehyde

Medical

Used together with lactic acid to produce the biodegradable and biocompatible poly(lactic-co-glycolic acid) copolymer for various medical applications, glycolic acid is an important component in chemical peeling procedures to reduce scarring and inflammation by skin exfoliation as well as to prevent pore clogging (<15 vol%).

Glycolic acid is also included in skin care creams and for the treatment of acne vulgaris at high concentrations, ~20-50 vol%, incorporated in chemical peelings to reduce acne-related inflammation (1).

With regard to chemical peeling of melasma, symmetrical hypermelanosis causing brown patches on the face, glycolic acid has shown better efficacy than phytic acid (2).

Glycolic acid has also shown potential as an endodontic agent for final irrigation in root canal therapy (3).

Cosmetics

α-Hydroxy acids are commonly used in creams and personal care products as anti-ageing substances and the results of this study showed improvement in epidermal and dermal structures (4). In addition, glycolic acid improves stratum corneum desquamation and induces biological responses that may help restore skin integrity (5).

Food industry

Aromatic agent and preservative.

Textile industry

Dyeing and tanning agent.

Other uses

• Included in emulsion polymers, additives and solvents for inks and paints with the primary task of improving gloss and flow properties.
• Adhesives and plastics.
• Effective for copper and aluminium metal finishing and cleaning applications.
• Industrial cleaners. Removes hard water scale deposits by forming water-soluble complexes that are easily rinsed off.
• Used in the cleaning of drinking water wells at a rate of 70%.
• Cleaning agent in industrial laundries.
• Disinfection. It is registered with the EPA for the use of active ingredients in liquid disinfectant formulations.

Safety

As with all α-hydroxy acids, glycolic acid is not free from adverse skin reactions such as itching, swelling or burning (6)..

Glycolic acid studies

Typical commercial product characteristics Glycolic acid

Appearance	White Crystalline Podwer or colourless liquid
Boiling Point	265.6±13.0°C at 760 mmHg
Melting Point	75-80°C
Flash Point	128.7±16.3°C
Density	1.4±0.1 g/cm3
Index of refraction	1.450
Free acid	≥ 62.0%
Water Insoluble	≤0.01%
Residue on ignition	≤0.3%
Ash	≤0.05%
Chloride as Cl	≤0.001%
Sulfates as SO4	≤0.05%
Iron	≤0.001%
Lead	≤0.001%
Arsenic	≤0.0002%
PSA	57.53000
LogP	-1.05
Storage	2-8°C
Safety

• Molecular Formula      C₂H₄O₃
• Linear Formula    HOCH₂COOH
• Exact Mass   76.016045
• Molecular Weight    76.05
• CAS  79-14-1
• UNII    0WT12SX38S
• EC Number   201-180-5
• DSSTox Substance ID  DTXSID0025363
• IUPAC  2-hydroxyacetic acid
• InChI=1S/C2H4O3/c3-1-2(4)5/h3H,1H2,(H,4,5)
• InChl Key      AEMRFAOFKBGASW-UHFFFAOYSA-N
• SMILES   C(C(=O)O)O
• MDL number  MFCD00004312
• PubChem Substance ID    24847624
• ChEBI  17497
• ICSC    1537
• NSC   166
• RTECS   MC5250000
• UN   3261
• RXCUI   587318
• eCl@ss   39021303
• Beilstein    1209322
• NACRES NA.21

Synonyms:

• Hydroxyacetic acid
• 2-Hydroxyacetic acid
• Hydroxyethanoic acid
• .alpha.-Hydroxyacetic acid
• Glycocide
• GLYCOLLATE
• Acetic acid, hydroxy-, homopolymer

References_________________________________________________________________

(1) Valle-González ER, Jackman JA, Yoon BK, Mokrzecka N, Cho NJ. pH-Dependent Antibacterial Activity of Glycolic Acid: Implications for Anti-Acne Formulations. Sci Rep. 2020 May 4;10(1):7491. doi: 10.1038/s41598-020-64545-9. 

(2) Sarkar R, Garg V, Bansal S, Sethi S, Gupta C. Comparative Evaluation of Efficacy and Tolerability of Glycolic Acid, Salicylic Mandelic Acid, and Phytic Acid Combination Peels in Melasma. Dermatol Surg. 2016 Mar;42(3):384-91. doi: 10.1097/DSS.0000000000000642.

(3) Bello YD, Porsch HF, Farina AP, Souza MA, Silva EJNL, Bedran-Russo AK, Cecchin D. Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects. Mater Sci Eng C Mater Biol Appl. 2019 Jul;100:323-329. doi: 10.1016/j.msec.2019.03.016. 

(4) Campione E, Cosio T, Lanna C, Mazzilli S, Dika E, Bianchi L. Clinical efficacy and reflectance confocal microscopy monitoring in moderate-severe skin aging treated with a polyvinyl gel containing retinoic and glycolic acid: An assessor-blinded 1-month study proof-of-concept trial. J Cosmet Dermatol. 2021 Jan;20(1):310-315. doi: 10.1111/jocd.13463. 

(5) Narda M, Trullas C, Brown A, Piquero-Casals J, Granger C, Fabbrocini G. Glycolic acid adjusted to pH 4 stimulates collagen production and epidermal renewal without affecting levels of proinflammatory TNF-alpha in human skin explants. J Cosmet Dermatol. 2021 Feb;20(2):513-521. doi: 10.1111/jocd.13570.

(6) Tang SC, Yang JH. Dual Effects of Alpha-Hydroxy Acids on the Skin. Molecules. 2018 Apr 10;23(4):863. doi: 10.3390/molecules23040863.