Benzoyl peroxide is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

(specifically, an

organic peroxide In organic chemistry, organic peroxides are organic compounds containing the peroxide functional group (). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily b ...

) with

structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bond ...

, often abbreviated as (BzO)₂. In terms of its structure, the molecule can be described as two

benzoyl In organic chemistry, benzoyl (, ) is the functional group with the formula C6H5CO-. It can be viewed as benzaldehyde missing one hydrogen. The term "benzoyl" should not be confused with benzyl, which has the formula C6H5CH2. The benzoyl group ...

(, Bz) groups connected by a

peroxide In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable. The most common peroxide is hydrogen p ...

(). It is a white granular solid with a faint odour of

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. ...

, poorly soluble in water but soluble in

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscibl ...

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

, and many other organic solvents. Benzoyl peroxide is an

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

, but it is principally used as in the production of polymers. Benzoyl peroxide is mainly used in production of

plastics Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptabi ...

and for bleaching

flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many cul ...

hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fi ...

and

textiles Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...

Synthesis, structure, and chemical reactivity

The original 1858 synthesis by Liebig reacted benzoyl chloride with barium peroxide, a reaction described by the following idealized equation: : Benzoyl peroxide is usually prepared by treating

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...

with benzoyl chloride under alkaline conditions. : As in many other peroxides, the C-O-O-C linkage has a dihedral angle near 90°. The oxygen–oxygen bond in peroxides is weak, although this weakness is not indicated by the O-O bond distance.. Thus, benzoyl peroxide undergoes homolysis (symmetrical fission), forming

free radicals In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spon ...

: : 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 Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...

of benzoyl peroxide is one hour at 92 °C. At 131 °C, the half-life is one minute. It has long been known that the compound has oxidizing properties. This property led to the use of BPO to treat various skin conditions, including

burn A burn is an injury to skin, or other tissues, caused by heat, cold, electricity, chemicals, friction, or ultraviolet radiation (like sunburn). Most burns are due to heat from hot liquids (called scalding), solids, or fire. Burns occur ma ...

s, chronic varicose leg tumors, and tinea sycosis. He also reported animal experiments that showed the relatively low toxicity of the compound. Treatment with benzoyl peroxide was proposed for wounds by Lyon and Reynolds in 1929, and for

sycosis vulgaris Sycosis vulgaris is a cutaneous condition characterized by a chronic infection of the chin or bearded region. The irritation is caused by a deep infection of hair follicles, often by species of ''Staphylococcus'' or ''Propionibacterium'' bacteria ...

and acne varioliformis by Peck and Chagrin in 1934. However, preparations were often of questionable quality. It was officially approved for the treatment of acne in the US in 1960.

Uses

Polymerization

Benzoyl peroxide is mainly used as a

radical initiator In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions. These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical i ...

to induce

chain-growth polymerization Chain-growth polymerization ( AE) or chain-growth polymerisation ( BE) is a polymerization technique where unsaturated monomer molecules add onto the active site on a growing polymer chain one at a time. There are a limited number of these acti ...

reactions, such as for

polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natura ...

and

poly(methyl methacrylate) Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylit ...

(PMMA) resins and

dental cement Dental cements have a wide range of dental and orthodontic applications. Common uses include temporary restoration of teeth, cavity linings to provide pulpal protection, sedation or insulation and cementing fixed prosthodontic appliances. Recent u ...

s and restoratives. It is the most important among the various

s used for this purpose, a relatively safe alternative to the much more hazardous methyl ethyl ketone peroxide. It is also used in rubber curing and as a finishing agent for some acetate yarns.

Other uses

Benzoyl peroxide is effective for treating acne lesions. It does not induce

antibiotic resistance Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistance. ...

. It may be combined with

salicylic acid Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substa ...

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

erythromycin Erythromycin is an antibiotic used for the treatment of a number of bacterial infections. This includes respiratory tract infections, skin infections, chlamydia infections, pelvic inflammatory disease, and syphilis. It may also be used durin ...

, or

clindamycin Clindamycin is an antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (middle ear in ...

(

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and preventio ...

), or

adapalene Adapalene is a third-generation topical retinoid primarily used in the treatment of mild-moderate acne, and is also used off-label to treat keratosis pilaris as well as other skin conditions. Studies have found adapalene is as effective as other ...

(a synthetic

retinoid The retinoids are a class of chemical compounds that are vitamers of vitamin A or are chemically related to it. Retinoids have found use in medicine where they regulate epithelial cell growth. Retinoids have many important functions throughout ...

). Two common

combination drug A combination drug or a fixed-dose combination (FDC) is a medicine that includes two or more active ingredients combined in a single dosage form. Terms like "combination drug" or "combination drug product" can be common shorthand for a FDC prod ...

s include benzoyl peroxide/clindamycin and adapalene/benzoyl peroxide,

being a chemically stable retinoid that can be combined with benzoyl peroxide unlike tezarotene and

tretinoin Tretinoin, also known as all-''trans'' retinoic acid (ATRA), is a medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For leukemia, it is taken by mouth f ...

. Combination products such as benzoyl peroxide/clindamycin and benzoyl peroxide/

appear to be slightly more effective than benzoyl peroxide alone for the treatment of acne lesions. The combination tretinoin/benzoyl peroxide was approved for medical use in the United States in 2021. 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%. No strong evidence supports the idea that higher concentrations of benzoyl peroxide are more effective than lower concentrations.

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 ''

Cutibacterium acnes ''Cutibacterium acnes'' (formerly ''Propionibacterium acnes'') is the relatively slow-growing, typically aerotolerant anaerobic, gram-positive bacterium (rod) linked to the skin condition of acne; it can also cause chronic blepharitis and endopht ...

'', the main

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

associated with acne. 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. Some evidence suggests that benzoyl peroxide has an anti-inflammatory effect as well. In micromolar concentrations it prevents neutrophils from releasing reactive oxygen species, part of the inflammatory response in acne. As a medication, benzoyl peroxide is mostly used to treat

acne Acne, also known as ''acne vulgaris'', is a long-term skin condition that occurs when dead skin cells and oil from the skin clog hair follicles. Typical features of the condition include blackheads or whiteheads, pimples, oily skin, and ...

, either alone or in combination with other treatments. Some versions are sold mixed with

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

s such as

. It is on the

WHO List of Essential Medicines Essential medicines, as defined by the World Health Organization (WHO), are the medicines that "satisfy the priority health care needs of the population". These are the medications to which people should have access at all times in sufficient a ...

, and, in the US, it is available as an

over-the-counter Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid prescr ...

and

generic medication A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active ...

. It is also used in

dentistry Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions of ...

for

teeth whitening Tooth whitening or tooth bleaching is the process of lightening the color of human teeth. Whitening is often desirable when teeth become yellowed over time for a number of reasons, and can be achieved by changing the intrinsic or extrinsic color o ...

Side effects

Application of benzoyl peroxide to the skin may result in redness, burning, and irritation. This side effect is dose-dependent. Because of these possible side effects, it is recommended to start with a low concentration and build up as appropriate, as the skin gradually develops

tolerance Tolerance or toleration is the state of tolerating, or putting up with, conditionally. Economics, business, and politics * Toleration Party, a historic political party active in Connecticut * Tolerant Systems, the former name of Veritas Software ...

to the medication. Skin sensitivity typically resolves after a few weeks of continuous use. Irritation can also be reduced by avoiding harsh facial cleansers and wearing

sunscreen Sunscreen, also known as sunblock or sun cream, is a photoprotective topical product for the skin that mainly absorbs, or to a much lesser extent reflects, some of the sun's ultraviolet (UV) radiation and thus helps protect against sunbur ...

prior to sun exposure. One in 500 people experience

hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. They are usually referred to as an over-reaction of the immune ...

to BPO and are liable to experience burning,

itching Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasan ...

, crusting, and possibly swelling. About one-third of people experience

phototoxicity Phototoxicity, also called photoirritation, is a chemically induced skin irritation, requiring light, that does not involve the immune system. It is a type of photosensitivity. The skin response resembles an exaggerated sunburn. The involved chemi ...

under exposure to

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

(UVB) light.

Other uses

As a

bleach Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to ...

, it has been used as a

medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and ...

and a water disinfectant. In specialized contexts, the name may be abbreviated as BPO. Benzoyl peroxide is used in dentistry as a

tooth whitening Tooth whitening or tooth bleaching is the process of lightening the color of human teeth. Whitening is often desirable when teeth become yellowed over time for a number of reasons, and can be achieved by changing the intrinsic or extrinsic color o ...

product.

Safety

Explosion hazard

Benzoyl peroxide is potentially

explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...

like other

s, 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.

Toxicity

Benzoyl peroxide breaks down in contact with skin, producing

benzoic acid Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin ...

and oxygen, neither of which is very toxic. With regards to BPO's

carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...

potential, one study concluded, "caution should be recommended in the use of this and other free radical-generating compounds". A 1999

IARC IARC may refer to: * International Aerial Robotics Competition * International Age Rating Coalition * International Agency for Research on Cancer * International Arctic Research Center * Israel Amateur Radio Club The Israel Amateur Radio Club ...

review of carcinogenicity studies found no evidence linking BPO acne medication to

skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...

s in humans. However, some animal studies found that the compound could act as a carcinogen and enhance the effect of known carcinogens.International Agency for Research on Cancer (1999): "Benzoyl peroxide". in
Re-evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide
''. Monographs on the Evaluation of Carcinogenic Risks to Humans, number 71, pages 345–358.

Skin irritation

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. The U.S.

National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...

has developed criteria for a recommended standard for occupational exposure to benzoyl peroxide.

Cloth staining

Contact with

fabric Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not ...

s or

, such as from still-moist acne medication, 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.

References

External links

* * * *
Organic Peroxide Producers Safety Division (OPPSD)
{{DEFAULTSORT:Benzoyl Peroxide Anti-acne preparations Benzene derivatives IARC Group 3 carcinogens Organic peroxides Radical initiators Wikipedia medicine articles ready to translate World Health Organization essential medicines