Benzoyl peroxide

Benzoyl peroxide (BPO or BzO2) is a medication and industrial chemical.[2] As a medication, it is used to treat mild to moderate acne.[3] For more severe cases, it may be used with other treatments.[3] Some versions are sold mixed with antibiotics such as clindamycin.[4] Other uses include bleaching flour, hair bleaching, teeth whitening, and textile bleaching.[5][6][7] It is also used in the plastic industry.[2]

Benzoyl peroxide
Skeletal formula (top) Ball-and-stick model (bottom)
Clinical data
Trade namesBenzac, Clearasil, PanOxyl, others
Other namesbenzoperoxide, dibenzoyl peroxide (DBPO)
AHFS/Drugs.comMultum Consumer Information
Pregnancy
category
  • US: C (Risk not ruled out)
    ATC code
    Identifiers
    CAS Number
    PubChem CID
    ChemSpider
    UNII
    KEGG
    ChEMBL
    E numberE928 (glazing agents, ...)
    CompTox Dashboard (EPA)
    ECHA InfoCard100.002.116
    Chemical and physical data
    FormulaC14H10O4
    Molar mass242.230 g·mol−1
    3D model (JSmol)
    Density1.334 g/cm3
    Melting point103 to 105 °C (217 to 221 °F) decomposes
    Solubility in waterpoor mg/mL (20 °C)
    See also: data page

    Common side effects are skin irritation, dryness, or peeling.[3][8] Use in pregnancy is of unclear safety.[9] Benzoyl peroxide is in the peroxide family of chemicals.[6] When used for acne, it works by killing bacteria.[5]

    Benzoyl peroxide was first made in 1905 and came into medical use in the 1930s.[5] It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.[10] Benzoyl peroxide is available as a generic medication and over the counter.[8] In the United Kingdom, 150 ml of a 10% solution cost the NHS about £4.[4] In the United States, a month of treatment costs less than US$25.[8]

    Uses

    Acne treatment
    Tube of a water-based 5% benzoyl peroxide preparation for the treatment of acne

    Benzoyl peroxide is effective for reducing the number and severity of acne lesions. It has a bactericidal effect on Cutibacterium acnes bacteria associated with acne and does not induce antibiotic resistance.[11][12] It may be combined with salicylic acid, sulfur, erythromycin or clindamycin (antibiotics), or adapalene (a synthetic retinoid). Two common combination drugs include benzoyl peroxide/clindamycin and adapalene/benzoyl peroxide, an unusual formulation considering most retinoids are deactivated by peroxides. Combination products such as benzoyl peroxide/clindamycin and benzoyl peroxide/salicylic acid appear to be slightly more effective than benzoyl peroxide alone for the treatment of acne lesions.[12]

    Benzoyl peroxide for acne treatment is typically applied to the affected areas in gel, cream, or liquid, in concentrations of 2.5% increasing through 5.0%, and up to 10%.[11] No strong evidence supports the idea that higher concentrations of benzoyl peroxide are more effective than lower concentrations.[11]

    Benzoyl peroxide commonly causes initial dryness and sometimes irritation, although the skin develops tolerance after a week or so. A small percentage of people are much more sensitive to it and liable to suffer burning, itching, crusting, and possibly swelling.[13] Applying the lowest concentration and building up as appropriate is most logical. Once tolerance is achieved, increasing the quantity or concentration and gaining tolerance at a higher level may give better subsequent acne clearance.[14] Irritation can also be reduced by avoiding harsh facial cleansers and wearing sunscreen prior to sun exposure.[14]

    Other uses

    Other common uses for benzoyl peroxide include:

    • Bleaching hair
    • Tooth whitening systems
    • The preparation of bleached flour
    • As a convenient oxidant in organic chemistry
    • An initiator and catalyst for polyester thermoset resins, as an alternative to the much more hazardous methyl ethyl ketone peroxide
    • A hardener to start the polymerization process in resins, for instance, PMMA resins can be polymerized with benzoyl peroxide.[15]
    • Removing ink and dye stains on vinyl dolls and other playscale figures.[16]

    In the U.S., the typical concentration for benzoyl peroxide is 2.5% to 10% for both prescription and over-the-counter drug preparations that are used in treatment for acne. Higher concentrations are used for hair bleach and teeth whitening. Benzoyl peroxide, like most peroxides, is a powerful bleaching agent. Contact with fabrics or hair can cause permanent color dampening almost immediately. Even secondary contact can cause bleaching; for example, contact with a towel that has been used to wash off benzoyl peroxide-containing hygiene products.[17] Benzoyl peroxide is also used as a radical initiator to induce chain-growth polymerization reactions,[18] and is the most important among the various organic peroxides used for this purpose.[19]

    Side effects

    Its application to the skin may result in redness, burning, and irritation. This side effect is dose-dependent. Skin sensitivity typically resolves after a few weeks of continuous use.[20] One in 500 people experience hypersensitivity[21] and about one-third of people experience phototoxicity to UVB.[22] It can bleach fabric, especially if it has not dried thoroughly.

    • Skin irritation due to benzoyl peroxide
    • A bleached fabric stain caused by contact with benzoyl peroxide

    Other

    Concentrated benzoyl peroxide is potentially explosive[23] like other organic peroxides, and can cause fires without external ignition. The hazard is acute for the pure material, so the compound is generally used as a solution or a paste. For example, cosmetics contain only a small percentage of benzoyl peroxide and pose no explosion risk.

    The carcinogenic potential of benzoyl peroxide has been investigated. A 1981 study published in the journal Science found that although benzoyl peroxide is not a carcinogen, it does promote cell growth when applied to an initiated tumor. The study concluded, "caution should be recommended in the use of this and other free radical-generating compounds".[24]

    In a 1977 study using a human maximization test, 76% of subjects acquired a contact sensitization to benzoyl peroxide. Formulations of 5% and 10% were used.[25]

    The U.S. National Institute for Occupational Safety and Health has developed criteria for a recommended standard for occupational exposure to benzoyl peroxide.[26]

    Mechanism of action

    Classically, benzoyl peroxide is thought to have a three-fold activity in treating acne. It is sebostatic, comedolytic, and inhibits growth of C. acnes.[27] In general, acne vulgaris is a hormone-mediated inflammation of sebaceous glands and hair follicles. Hormone changes cause an increase in keratin and sebum production, leading to blocked drainage. C. acnes has many lytic enzymes that break down the proteins and lipids in the sebum, leading to an inflammatory response. The free-radical reaction of benzoyl peroxide can break down the keratin, therefore unblocking the drainage of sebum (comedolytic). It can cause nonspecific peroxidation of C. acnes, making it bactericidal, and it was thought to decrease sebum production, but disagreement exists within the literature on this.[20][27]

    Anti-inflammatory

    Some evidence suggests that benzoyl peroxide has an anti-inflammatory effect, as well. Micromolar concentrations it prevent neutrophils from releasing reactive oxygen species, part of the inflammatory response in acne.[20]

    Chemistry

    It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is (C6H5CO)2O2. It is one of the most important organic peroxides in terms of applications and the scale of its production.

    Benzoyl peroxide was the first organic peroxide prepared by intentional synthesis. It was prepared by treating benzoyl chloride with barium peroxide,[28] a reaction that probably follows this equation:

    2 C6H5C(O)Cl + BaO2 → (C6H5CO)2O2 + BaCl2

    Benzoyl peroxide is usually prepared by treating hydrogen peroxide with benzoyl chloride.

    2 C6H5COCl + H2O2 + 2 NaOH → (C6H5CO)2O2 + 2 NaCl + 2 H2O

    The oxygen–oxygen bond in peroxides is weak. Thus, benzoyl peroxide readily undergoes homolysis (symmetrical fission), forming free radicals:

    (C6H5CO)2O2 → 2 C
    6    H
    5    CO•
    2

    The symbol • indicates that the products are radicals; i.e., they contain at least one unpaired electron. Such species are highly reactive. The homolysis is usually induced by heating. The half-life of benzoyl peroxide is one hour at 92 °C. At 131 °C, the half-life is one minute.[29]

    Benzoyl peroxide breaks down in contact with skin, producing benzoic acid and oxygen, neither of which is very toxic.[30]

    References
    1. IUPAC Chemical Nomenclature and Structure Representation Division (2013). "P-65.7.5". In Favre, Henri A.; Powell, Warren H. (eds.). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. IUPAC–RSC. ISBN 978-0-85404-182-4.
    2. Stellman, Jeanne Mager (1998). Encyclopaedia of Occupational Health and Safety: Guides, indexes, directory. International Labour Organization. p. 104. ISBN 9789221098171. Archived from the original on 2017-09-18.
    3. WHO Model Formulary 2008 (PDF). World Health Organization. 2009. pp. 307–308. ISBN 9789241547659. Archived (PDF) from the original on 13 December 2016. Retrieved 8 January 2017.
    4. British national formulary : BNF 69 (69 ed.). British Medical Association. 2015. p. 820. ISBN 9780857111562.
    5. Plewig, G.; Kligman, A. M. (2012). ACNE and ROSACEA (3 ed.). Springer Science & Business Media. p. 613. ISBN 9783642597152. Archived from the original on 2017-09-18.
    6. Pommerville, Glendale Community College Jeffrey C.; Pommerville, Jeffrey (2012). Alcamo's Fundamentals of Microbiology: Body Systems. Jones & Bartlett Publishers. p. 214. ISBN 9781449605957. Archived from the original on 2017-09-18.
    7. Braun-Falco, Otto; Plewig, Gerd; Wolff, Helmut Heinrich; Burgdorf, Walter (2012). Dermatology (2 ed.). Springer Science & Business Media. p. 1039. ISBN 9783642979316. Archived from the original on 2017-09-18.
    8. Hamilton, Richart (2015). Tarascon Pocket Pharmacopoeia 2015 Deluxe Lab-Coat Edition. Jones & Bartlett Learning. p. 173. ISBN 9781284057560.
    9. "Benzoyl Peroxide topical Use During Pregnancy | Drugs.com". www.drugs.com. Archived from the original on 16 January 2017. Retrieved 13 January 2017.
    10. "WHO Model List of Essential Medicines (19th List)" (PDF). World Health Organization. April 2015. Archived (PDF) from the original on 13 December 2016. Retrieved 8 December 2016.
    11. Simonart, T. (December 2012). "Newer approaches to the treatment of acne vulgaris". Am. J. Clin. Dermatol. 13 (6): 357–64. doi:10.2165/11632500-000000000-00000. PMID 22920095.
    12. Seidler, E. M.; Kimball, A. B. (July 2010). "Meta-analysis comparing efficacy of benzoyl peroxide, clindamycin, benzoyl peroxide with salicylic acid, and combination benzoyl peroxide/clindamycin in acne". J. Am. Acad. Dermatol. 63 (1): 52–62. doi:10.1016/j.jaad.2009.07.052. PMID 20488582.
    13. "Benzoyl peroxide". Mayo Clinic. January 1, 2016. Archived from the original on July 18, 2016.
    14. Alldredge, Brian K., ed. (2013). Applied Therapeutics: The Clinical Use of Drugs (10th ed.). Baltimore: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 949. ISBN 978-1609137137.
    15. "Error - Evonik Industries AG" (PDF).
    16. Stevens, Cynthia. "Oxy10 for vinyl stains. Benzoyl peroxide removes stain from vinyl. Restore Dolls". Prilly Charmin Dolls. Archived from the original on 31 August 2015. Retrieved 9 February 2015.
    17. Bojar, R. A.; Cunliffe, William; Holland, K. T. (1995), "The short-term treatment of acne vulgaris with benzoyl peroxide: effects on the surface and follicular cutaneous microflora", Br. J. Dermatol., 132 (2): 204–8, doi:10.1111/j.1365-2133.1995.tb05014.x, PMID 7888356
    18. Klenk, Herbert; Götz, Peter H.; Siegmeier, Rainer; Mayr, Wilfried. "Peroxy Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_199.
    19. "Initiation By Diacyl Peroxides". Polymer Properties Database. Retrieved October 19, 2018.
    20. Worret, Wolf-Ingo; Fluhr, Joachim W. (2006-04-01). "[Acne therapy with topical benzoyl peroxide, antibiotics and azelaic acid]". Journal der Deutschen Dermatologischen Gesellschaft. 4 (4): 293–300. doi:10.1111/j.1610-0387.2006.05931.x. ISSN 1610-0379. PMID 16638058.
    21. Cunliffe, W. J.; Burke, B. (1982-01-01). "Benzoyl peroxide: lack of sensitization". Acta Dermato-Venereologica. 62 (5): 458–459. ISSN 0001-5555. PMID 6183909.
    22. Jeanmougin, M.; Pedreiro, J.; Bouchet, J.; Civatte, J. (1983-01-01). "[Phototoxic activity of 5% benzoyl peroxide in man. Use of a new methodology]". Dermatologica. 167 (1): 19–23. ISSN 0011-9075. PMID 6628794.
    23. Cartwright, Hugh (17 March 2005). "Chemical Safety Data: Benzoyl peroxide". Oxford University. Archived from the original on 12 October 2010. Retrieved 13 August 2011.
    24. Slaga, TJ; Klein-Szanto, AJ; Triplett, LL; Yotti, LP; Trosko, KE (2012-05-24). "Skin tumor-promoting activity of benzoyl peroxide, a widely used free radical-generating compound". Science. 213 (4511): 1023–5. Bibcode:1981Sci...213.1023S. doi:10.1126/science.6791284. PMID 6791284.
    25. Leyden, James J.; Kligman, Albert M. (1977), "Contact sensitization to benzoyl peroxide", Contact Dermatitis, 3 (5): 273–75, doi:10.1111/j.1600-0536.1977.tb03674.x, PMID 145346
    26. "Criteria for a Recommended Standard: Occupational Exposure to Benzoyl Peroxide (77-166)". CDC - NIOSH Publications and Products. June 6, 2014. doi:10.26616/NIOSHPUB76128. Archived from the original on August 9, 2016. Retrieved 2016-07-15.
    27. Cotterill, J. A. (1980-01-01). "Benzoyl peroxide". Acta Dermato-Venereologica. Supplementum. Suppl 89: 57–63. ISSN 0365-8341. PMID 6162349.
    28. Brodie, B. C. (1858), "Ueber die Bildung der Hyperoxyde organischer Säureradicale" [On the Formation of the Peroxides of Organic Acid Radicals], Justus Liebigs Ann. Chem., 108: 79–83, doi:10.1002/jlac.18581080117
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