This article is about antimicrobial agents. For the Macintosh anti-virus software, see Disinfectant (software).
Disinfection of a floor using disinfectant liquid applied using a mop.
Levels of resistance of microbes to disinfectants.

Disinfectants are antimicrobial agents that are applied to the surface of non-living objects to destroy microorganisms that are living on the objects.[1] Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than sterilization, which is an extreme physical and/or chemical process that kills all types of life.[1] Disinfectants are different from other antimicrobial agents such as antibiotics, which destroy microorganisms within the body, and antiseptics, which destroy microorganisms on living tissue. Disinfectants are also different from biocides — the latter are intended to destroy all forms of life, not just microorganisms. Disinfectants work by destroying the cell wall of microbes or interfering with the metabolism.

Sanitizers are substances that simultaneously clean and disinfect.[2] Disinfectants are frequently used in hospitals, dental surgeries, kitchens, and bathrooms to kill infectious organisms.

Bacterial endospores are most resistant to disinfectants, but some viruses and bacteria also possess some tolerance.

In wastewater treatment, a disinfection step with chlorine, ultra-violet (UV) radiation or ozonation can be included as tertiary treatment to remove pathogens from wastewater, for example if it is to be reused to irrigate golf courses. An alternative term used in the sanitation sector for disinfection of waste streams, sewage sludge or fecal sludge is sanitisation or sanitization.


A perfect disinfectant would also offer complete and full microbiological sterilisation, without harming humans and useful form of life, be inexpensive, and noncorrosive. However, most disinfectants are also, by nature, potentially harmful (even toxic) to humans or animals. Most modern household disinfectants contain Bitrex, an exceptionally bitter substance added to discourage ingestion, as a safety measure. Those that are used indoors should never be mixed with other cleaning products as chemical reactions can occur.[3] The choice of disinfectant to be used depends on the particular situation. Some disinfectants have a wide spectrum (kill many different types of microorganisms), while others kill a smaller range of disease-causing organisms but are preferred for other properties (they may be non-corrosive, non-toxic, or inexpensive).[4] There are arguments for creating or maintaining conditions that are not conducive to bacterial survival and multiplication, rather than attempting to kill them with chemicals. Bacteria can increase in number very quickly, which enables them to evolve rapidly. Should some bacteria survive a chemical attack, they give rise to new generations composed completely of bacteria that have resistance to the particular chemical used. Under a sustained chemical attack, the surviving bacteria in successive generations are increasingly resistant to the chemical used, and ultimately the chemical is rendered ineffective. For this reason, some question the wisdom of impregnating cloths, cutting boards and worktops in the home with bactericidal chemicals.


Air disinfectants

Air disinfectants are typically chemical substances capable of disinfecting microorganisms suspended in the air. Disinfectants are generally assumed to be limited to use on surfaces, but that is not the case. In 1928, a study found that airborne microorganisms could be killed using mists of dilute bleach.[5] An air disinfectant must be dispersed either as an aerosol or vapour at a sufficient concentration in the air to cause the number of viable infectious microorganisms to be significantly reduced.

In the 1940s and early 1950s, further studies showed inactivation of diverse bacteria, influenza virus, and Penicillium chrysogenum (previously P. notatum) mold fungus using various glycols, principally propylene glycol and triethylene glycol.[6] In principle, these chemical substances are ideal air disinfectants because they have both high lethality to microorganisms and low mammalian toxicity.[7][8]

Although glycols are effective air disinfectants in controlled laboratory environments, it is more difficult to use them effectively in real-world environments because the disinfection of air is sensitive to continuous action. Continuous action in real-world environments with outside air exchanges at door, HVAC, and window interfaces, and in the presence of materials that adsorb and remove glycols from the air, poses engineering challenges that are not critical for surface disinfection. The engineering challenge associated with creating a sufficient concentration of the glycol vapours in the air have not to date been sufficiently addressed.[9][10]


Alcohol and alcohol plus Quaternary ammonium cation based compounds comprise a class of proven surface sanitizers and disinfectants approved by the EPA and the Centers for Disease Control for use as a hospital grade disinfectant.[11] Alcohols are most effective when combined with distilled water to facilitate diffusion through the cell membrane; 100% alcohol typically denatures only external membrane proteins.[12] A mixture of 70% ethanol or isopropanol diluted in water is effective against a wide spectrum of bacteria, though higher concentrations are often needed to disinfect wet surfaces.[13] Additionally, high-concentration mixtures (such as 80% ethanol + 5% isopropanol) are required to effectively inactivate lipid-enveloped viruses (such as HIV, hepatitis B, and hepatitis C).[12][13][14][14][15] The efficacy of alcohol is enhanced when in solution with the wetting agent dodecanoic acid (coconut soap). The synergistic effect of 29.4% ethanol with dodecanoic acid is effective against a broad spectrum of bacteria, fungi, and viruses. Further testing is being performed against Clostridium difficile (C.Diff) spores with higher concentrations of ethanol and dodecanoic acid, which proved effective with a contact time of ten minutes.[16]


Aldehydes, such as formaldehyde and glutaraldehyde, have a wide microbiocidal activity and are sporicidal and fungicidal. They are partly inactivated by organic matter and have slight residual activity.

Some bacteria have developed resistance to glutaraldehyde, and it has been found that glutaraldehyde can cause asthma and other health hazards, hence ortho-phthalaldehyde is replacing glutaraldehyde.

Oxidizing agents

Oxidizing agents act by oxidizing the cell membrane of microorganisms, which results in a loss of structure and leads to cell lysis and death. A large number of disinfectants operate in this way. Chlorine and oxygen are strong oxidizers, so their compounds figure heavily here.


Phenolics are active ingredients in some household disinfectants. They are also found in some mouthwashes and in disinfectant soap and handwashes. Phenols are toxic to cats[21] and newborn humans[22]

Quaternary ammonium compounds

Quaternary ammonium compounds ("quats"), such as benzalkonium chloride, are a large group of related compounds. Some concentrated formulations have been shown to be effective low-level disinfectants. Quaternary Ammonia at or above 200ppm plus Alcohol solutions exhibit efficacy against difficult to kill non-enveloped viruses such as norovirus, rotavirus, or polio virus.[11] Newer synergous, low-alcohol formulations are highly effective broad-spectrum disinfectants with quick contact times (3–5 minutes) against bacteria, enveloped viruses, pathogenic fungi, and mycobacteria. Quats are biocides that also kill algae and are used as an additive in large-scale industrial water systems to minimize undesired biological growth.


Silver has antimicrobial properties, but compounds suitable for disinfection are usually unstable and have a limited shelf-life. Silver dihydrogen citrate (SDC) is a chelated form of silver that maintains its stability. SDC kills microorganisms by two modes of action: 1) the silver ion deactivates structural and metabolic membrane proteins, leading to microbial death; 2) the microbes view SDC as a food source, allowing the silver ion to enter the microbe. Once inside the organism, the silver ion denatures the DNA, which halts the microbe's ability to replicate, leading to its death. This dual action makes SDC highly and quickly effective against a broad spectrum of microbes. SDC is non-toxic, non-caustic, colorless, odorless, and tasteless, and does not produce toxic fumes. SDC is non-toxic to humans and animals: the United States Environmental Protection Agency classifies it into the lowest toxicity category for disinfectants, category IV.

A meta-analysis of 26 studies by the Cochrane Collaboration found that, most were small and of poor quality, and that there was not enough evidence to support the use of silver-containing dressings or creams, as generally these treatments did not promote wound healing or prevent wound infections. Some evidence suggested that silver sulphadiazine had no effect on infection, and actually slowed healing.[23]

Copper alloy surfaces

Copper-alloy surfaces have natural intrinsic properties to destroy a wide range of microorganisms (e.g., E. coli O157:H7, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi). In addition, extensive tests on E. coli O157:H7, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus, Enterobacter aerogenes, and Pseudomonas aeruginosa sanctioned by the United States Environmental Protection Agency (EPA) using Good Laboratory Practices found that when cleaned regularly, some 355 different copper alloy surfaces:

These copper alloys were granted EPA registrations as "antimicrobial materials with public health benefits,"[24] which allows manufacturers to legally make claims regarding the positive public health benefits of products made with registered antimicrobial copper alloys. EPA has approved a long list of antimicrobial copper products made from these alloys, such as bedrails, handrails, over-bed tables, sinks, faucets, door knobs, toilet hardware, computer keyboards, health club equipment, shopping cart handles, etc. (for a comprehensive list of products, see: Antimicrobial copper-alloy touch surfaces#Approved products). Antimicrobial copper alloy products are now being installed in healthcare facilities in the U.K., Ireland, Japan, Korea, France, Denmark, and Brazil and in the subway transit system in Santiago, Chile, where copper-zinc alloy handrails will be installed in some 30 stations between 2011 and 2014.[25]

Thymol-based disinfectant

Thymol, a phenolic chemical found in thyme, can be as effective as bleach in terms of disinfecting as both are considered an intermediate level disinfectant.[26] Thyme essential oils have bacteriostatic activity against a variety of microorganisms,[27] including E. coli and S. aureus.[28]


The biguanide polymer polyaminopropyl biguanide is specifically bactericidal at very low concentrations (10 mg/l). It has a unique method of action: The polymer strands are incorporated into the bacterial cell wall, which disrupts the membrane and reduces its permeability, which has a lethal effect to bacteria. It is also known to bind to bacterial DNA, alter its transcription, and cause lethal DNA damage.[29] It has very low toxicity to higher organisms such as human cells, which have more complex and protective membranes.

Ultraviolet germicidal irradiation is the use of high-intensity shortwave ultraviolet light for disinfecting smooth surfaces such as dental tools, but not porous materials that are opaque to the light such as wood or foam. Ultraviolet light is also used for municipal water treatment. Ultraviolet light fixtures are often present in microbiology labs, and are activated only when there are no occupants in a room (e.g., at night).

Common sodium bicarbonate (NaHCO3) has antifungal properties,[30] and some antiviral and antibacterial properties,[31] though those are too weak to be effective at a home environment.[32]

Lactic acid is a registered disinfectant. Due to its natural and environmental profile, it has gained importance in the market.

Measurements of effectiveness

One way to compare disinfectants is to compare how well they do against a known disinfectant and rate them accordingly. Phenol is the standard, and the corresponding rating system is called the "Phenol coefficient". The disinfectant to be tested is compared with phenol on a standard microbe (usually Salmonella typhi or Staphylococcus aureus). Disinfectants that are more effective than phenol have a coefficient > 1. Those that are less effective have a coefficient < 1.

The standard European approach for disinfectant validation consists of a basic suspension test, a quantitative suspension test (with low and high levels of organic material added to act as ‘interfering substances’) and a two part simulated-use surface test.[33]

A less specific measurement of effectiveness is the United States Environmental Protection Agency (EPA) classification into either high, intermediate or low levels of disinfection. "High-level disinfection kills all organisms, except high levels of bacterial spores" and is done with a chemical germicide marketed as a sterilant by the U.S. Food and Drug Administration (FDA). "Intermediate-level disinfection kills mycobacteria, most viruses, and bacteria with a chemical germicide registered as a 'tuberculocide' by the Environmental Protection Agency. Low-level disinfection kills some viruses and bacteria with a chemical germicide registered as a hospital disinfectant by the EPA."[34]

An alternative assessment is to measure the Minimum inhibitory concentrations (MICs) of disinfectants against selected (and representative) microbial species, such as through the use of microbroth dilution testing.[35]

Home disinfectants

Doors at the Hong Kong Museum of History with signage stating that the doors are disinfected frequently.

By far the most cost-effective home disinfectant is the commonly used chlorine bleach (a 5% solution of sodium hypochlorite), which is effective against most common pathogens, including difficult organisms such as tuberculosis (mycobacterium tuberculosis), hepatitis B and C, fungi, and antibiotic-resistant strains of staphylococcus and enterococcus. It even has some disinfectant action against parasitic organisms.[36]

Positives are that it kills the widest range of pathogens of any inexpensive disinfectant, is extremely powerful against viruses and bacteria at room temperature, is commonly available and inexpensive, and breaks down quickly into harmless components (primarily table salt and oxygen).

Negatives are that it is caustic to the skin, lungs, and eyes (especially at higher concentrations); like many common disinfectants, it degrades in the presence of organic substances; it has a strong odor; it is not effective against Giardia lamblia and Cryptosporidium; and extreme caution must be taken not to combine it with ammonia or any acid (such as vinegar), as this can cause noxious gases to be formed. The best practice is not to add anything to household bleach except water.

To use chlorine bleach effectively, the surface or item to be disinfected must be clean. In the bathroom or when cleaning after pets, special caution must be taken to wipe up urine first, before applying chlorine, to avoid reaction with the ammonia in urine, causing toxic gas by-products. A 1-to-20 solution in water is effective simply by being wiped on and left to dry. The user should wear rubber gloves and, in tight airless spaces, goggles. If parasitic organisms are suspected, it should be applied at 1-to-1 concentration, or even undiluted. Extreme caution must be taken to avoid contact with eyes and mucous membranes. Protective goggles and good ventilation are mandatory when applying concentrated bleach.

Commercial bleach tends to lose strength over time, whenever the container is opened. Old containers of partially used bleach may no longer have the labeled concentration.

Where one does not want to risk the corrosive effects of bleach, alcohol-based disinfectants are reasonably inexpensive and quite safe. The great drawback to them is their rapid evaporation; sometimes effective disinfection can be obtained only by immersing an object in the alcohol.

The use of some antimicrobials such as triclosan, in particular in the uncontrolled home environment, is controversial because it may lead to the germs becoming resistant. Chlorine bleach and alcohol do not cause resistance because they are so completely lethal, in a very direct physical way.[37]

See also


  1. 1 2 "Division of Oral Health - Infection Control Glossary". U.S. Centers for Disease Control and Prevention. Retrieved 19 April 2016.
  2. Cleaning and disinfecting, (2009), Mid Sussex District Council, UK.
  3. "Common Cleaning Products May Be Dangerous When Mixed" (PDF). New Jersey Department of Health and Senior Services. Retrieved 19 April 2016.
  4. "Hospital Disinfectants for General Disinfection of Environmental Surfaces" (PDF). New York State Department of Health. Retrieved 19 April 2016.
  5. For a review of the early work in this field, see: Robertson OH, Bigg E, Puck TT, Miller BF (June 1942). "The bactericidal action of propylene glycol vapor on microorganisms suspended in air. i". Journal of Experimental Medicine. 75 (6): 593–610. doi:10.1084/jem.75.6.593. PMC 2135271Freely accessible. PMID 19871209.
  6. For a review through 1952 see: Lester W, Dunklin E, Robertson OH (April 1952). "Bactericidal effects of propylene and triethylene glycol vapors on airborne Escherichia coli". Science. 115 (2988): 379–382. doi:10.1126/Science.115.2988.379. PMID 17770126.
  7. For a review of the toxicity of propylene glycol, see: United States Environmental Protection Agency (September 2006). "Reregistration eligibility decision for propylene glycol and dipropylene glycol". EPA 739-R-06-002.
  8. For a review of the toxicity of triethylene glycol, see: United States Environmental Protection Agency (September 2005). "Reregistration eligibility decision for triethylene glycol". EPA 739-R-05-002.
  9. Committee on Research Standards (May 1950). "Air Sanitation (Progress in the Control of Air-Borne Infections)". American Journal of Public Health and the Nation's Health. 40 (5 Pt 2): 82–88. doi:10.2105/AJPH.40.5_Pt_2.82. PMC 1528669Freely accessible. PMID 15418852.
  10. Lester W, Kaye S, Robertson OH, Dunklin EW (July 1950). "Factors of Importance in the Use of Triethylene Glycol Vapor for Aerial Disinfection". American Journal of Public Health and the Nation's Health. 40 (7): 813–820. doi:10.2105/AJPH.40.7.813. PMC 1528959Freely accessible. PMID 15425663.
  11. 1 2 https://www.cdc.gov/hicpac/Disinfection_Sterilization/6_0disinfection.html
  12. 1 2 FDA/CFSAN - Food Safety A to Z Reference, "Bacteria" http://vm.cfsan.fda.gov/~dms/a2z-b.html
  13. 1 2 Moorer WR (August 2003). "Antiviral activity of alcohol for surface disinfection". International Journal of Dental Hygiene. 1 (3): 138–42. doi:10.1034/j.1601-5037.2003.00032.x. PMID 16451513.
  14. 1 2 van Engelenburg FA, Terpstra FG, Schuitemaker H, Moorer WR (June 2002). "The virucidal spectrum of a high concentration alcohol mixture". The Journal of Hospital Infection. 51 (2): 121–5. doi:10.1053/jhin.2002.1211. PMID 12090799.
  15. Lages SL, Ramakrishnan MA, Goyal SM (February 2008). "In-vivo efficacy of hand sanitisers against feline calicivirus: a surrogate for norovirus". The Journal of Hospital Infection. 68 (2): 159–63. doi:10.1016/j.jhin.2007.11.018. PMID 18207605.
  16. "Clean & Disinfect Mold, Bacteria & Viruses in any Environment". Retrieved 2010-11-18.
  17. Weber DJ, Barbee SL, Sobsey MD, Rutala WA (December 1999). "The effect of blood on the antiviral activity of sodium hypochlorite, a phenolic, and a quaternary ammonium compound". Infection Control and Hospital Epidemiology. 20 (12): 821–7. doi:10.1086/501591. PMID 10614606.
  18. "CDC - Immediately Dangerous to Life or Health Concentrations (IDLH): Chemical Listing and Documentation of Revised IDLH Values - NIOSH Publications and Products". Cdc.gov. 2009-07-31. Retrieved 2012-11-10.
  19. Omidbakhsh; et al. (2006). "A new peroxide-based flexible endoscope-compatible high-level disinfectant". American Journal of Infection Control. 34 (9): 571–577. doi:10.1016/j.ajic.2006.02.003. PMID 17097451.
  20. Sattar; et al. (Winter 1998). "A product based on accelerated hydrogen peroxide: Evidence for broad-spectrum activity". Canadian Journal of Infection Control: 123–130.
  21. http://www.peteducation.com/article.cfm?c=2+1677&aid=2243
  22. https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+113
  23. Storm-Versloot MN; Vos CG; Ubbink DT; Vermeulen H (17 March 2010). "Probably that silver-containing dressings and creams do not prevent wound infection or promote healing". Cochrane. Retrieved 19 April 2016.
  24. EPA registers copper-containing alloy products, May 2008
  25. A. Samuel (2011-07-22). "Chilean subway protected with Antimicrobial Copper - Rail News from". rail.co. Retrieved 2012-11-10.
  26. http://www.education.nh.gov/instruction/school_health/documents/disinfectants.pdf
  27. Marino, Marilena; Bersani, Carla; Comi, Giuseppe (1999). "Antimicrobial Activity of the Essential Oils of Thymus vulgaris L. Measured Using a Bioimpedometric Method". Journal of Food Protection (9): 1017–1023.
  28. http://www.bccdc.ca/NR/rdonlyres/E9C003D1-E781-498B-9210-E3E6A623D96C/0/EHSeminarDec122011_Alternative_antimicrobial_agents.pdf
  29. Allen MJ, White GF, Morby AP (2006). "The response of Escherichia coli to exposure to the biocide polyhexamethylene biguanide". Microbiology (Reading, Engl.). 152 (Pt 4): 989–1000. doi:10.1099/mic.0.28643-0. PMID 16549663.
  30. Zamani M, Sharifi Tehrani A, Ali Abadi AA (2007). "Evaluation of antifungal activity of carbonate and bicarbonate salts alone or in combination with biocontrol agents in control of citrus green mold". Communications in Agricultural and Applied Biological Sciences. 72 (4): 773–7. PMID 18396809.
  31. Malik YS, Goyal SM (May 2006). "Virucidal efficacy of sodium bicarbonate on a food contact surface against feline calicivirus, a norovirus surrogate". International Journal of Food Microbiology. 109 (1–2): 160–3. doi:10.1016/j.ijfoodmicro.2005.08.033. PMID 16540196.
  32. William A. Rutala; Susan L. Barbee; Newman C. Aguiar; Mark D. Sobsey; David J. Weber (2000). "Antimicrobial Activity of Home Disinfectants and Natural Products Against Potential Human Pathogens". Infection Control and Hospital Epidemiology. The University of Chicago Press on behalf of The Society for Healthcare Epidemiology of America. 21 (1): 33–38. doi:10.1086/501694. JSTOR 10. PMID 10656352.
  33. Sandle T (editor) (2012). The CDC Handbook: A Guide to Cleaning and Disinfecting Cleanrooms (1st ed.). Grosvenor House Publishing Limited. ISBN 978-1781487686.
  34. Centers for Disease Control and Prevention (December 21, 2012). "Sterilization or Disinfection of Medical Devices". CDC. Retrieved July 20, 2013.
  35. Vijayakumar R, Kannan VV, Sandle T, Manoharan C. (May 2012). "In vitro Antifungal Efficacy of Biguanides and Quaternary Ammonium Compounds against Cleanroom Fungal Isolates". PDA J Pharm Sci Technol. 66 (3): 236–42. doi:10.5731/pdajpst.2012.00866.
  36. EPA's Registered Sterilizers, Tuberculocides, and Antimicrobial Products Against HIV-1, and Hepatitis B and Hepatitis C Viruses. (Obtained January 4, 2006)
  37. "Antimicrobial Products: Who Needs Them? — Washington Toxics Coalition". Watoxics.org. 1997-09-15. Retrieved 2012-11-10.

Further reading

External links

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