Antiseptics and disinfectants are used extensively in hospitals and other healthcare settings for a variety of topical and hard-surface applications. In particular, they are an essential part of infection control practices and aid in the prevention of nosocomial infections. Mounting concerns over the potential for microbial contamination and infection risks in the food and general consumer markets have also led to increased use of antiseptics and disinfectants by the general public. A wide variety of active chemical agents (or “biocides”) are found in these products, many of which have been used for hundreds of years for antisepsis, disinfection, and preservation. Despite this, less is known about the mode of action of these active agents than about antibiotics. In general, biocides have a broader spectrum of activity than antibiotics, and, while antibiotics tend to have specific intracellular targets, biocides may have multiple targets. The widespread use of antiseptic and disinfectant products has prompted some speculation on the development of microbial resistance, in particular cross-resistance to antibiotics.

Antiseptics are antimicrobial substances which are applied to the skin to inhibit the action of microorganisms. Antiseptic such as Chlorhexidine carries a positively charged hydrophobic and lipophilic molecule which can interact with phospholipids and lipopolysaccharides (LPS) molecules present in the cell membrane of the microorganism. This interaction disturbs the osmotic equilibrium of cell and increases the cell membrane which allows the reactant molecule to enter the cell and cause damage.

Types of antiseptic

Antiseptics can be classified according to their chemical structure. Commonly used antiseptic groups include:
1. Alcohol: Alcohols like ethanol, propanol, and mixtures of alcohols act as good antiseptics. These alcoholic solutions are commonly used for disinfection of skin
2. Quaternary ammonium compound: These compounds can be used as antibiotic as well as antiseptics They are commonly abbreviated as ‘QUATS’ and are used to sterilize skin, to preserve eye drops and for irrigation purpose.
3. Chlorhexidine and other diguanide: It is a biguanidine derivative of chlorhexidine widely used as pre-operative skin disinfectant, to treat wounds, for gingivitis, and for bladder irrigation.
4. Antibacterial dye: as skin disinfectant and to treat a wound or burn. Brilliant Green is a triarylmethane dye used for treatment of small wounds and skin abscess
5. Peroxide and permanganate: Hydrogen peroxide solution acts as good antiseptic due to its oxidizing nature. It is used to clean wounds, ulcers, disinfect skin, as a gargle or mouthwash and for irrigation.
6. Phenol derivative: Used as an antiseptic baby powder, skin disinfectant and in medicated soap and solution, used in mouthwashes and throat lozenges
7. Quinolone derivative: Used to treat wounds, in throat lozenges and as a skin disinfectant
8. Iodine: Good antiseptic used for skin disinfection, and treatment of minor wounds. Cadexomer iodide can be used as an ointment or a dressing.

Disinfection is the process of inactivating or killing harmful bacteria, cysts and other pathogenic microorganisms by various agents such as heat, chemicals, ultraviolet light, ultrasonic waves, or radiation. Disinfection is used extensively in the water industry and chemistry/environmental industry and the below definition is related to that field. Disinfection is the killing of many, but not all microorganisms. It is a process in which the number of contaminating organisms is reduced to a level that cannot cause infection, i.e. pathogens must be killed but some organisms and bacterial spores may survive.

Disinfectants are antimicrobial agents which are applied to destroy microbes from the surface of non-living objects.
A good disinfectant would provide complete and full sterilization against microorganisms without affecting human and other useful lifeforms. Different types of disinfectants are used in different industries which aim at the specific microbial flora. Some disinfectants can kill many different types (wide spectrum); while others kill a smaller range of disease-causing microorganisms but are preferred for other properties (they may be non-corrosive, non-toxic, or inexpensive). The method of disinfection is used globally for the safety of humans, to decrease the scale of diseases transmission. A large significance of sterilization and disinfection has been placed in the food industry, water sanitation and medical care and hospitals.

Methods of disinfection
The methods used for disinfection are:
1. Physical disinfection (by heat, filtration or radiation)
2. Chemical disinfection

Types of Disinfectants

1. Air disinfectants
Air disinfectants are chemical substances used to kill airborne microorganisms. Air disinfectants such as glycols (propylene glycol and triethylene glycol) are considered to be ideal disinfectants because of their lethality to a range of microorganisms such as bacteria, influenza virus, and mold fungus and low mammalian toxicity. These chemicals must be dispersed either as an aerosol or vapor in the air at a sufficient concentration to reduce infectious microbial flora.

2. Alcohols
Alcohols in combination with distilled water are most effective to facilitate diffusion through the cell membrane. Higher concentration is often used to disinfect wet surfaces
100% alcohol – denature only external membrane proteins.
70% alcohol or diluted Isopropanol – effective against wide range of bacteria
80% ethanol + 5% isopropanol- inactivate lipid-enveloped viruses (such as HIV, hepatitis B, and hepatitis C)
29.4% ethanol with dodecanoic acid- effective against many bacteria, fungi, and viruses.

3. Aldehydes
Aldehydes, such as formaldehyde and glutaraldehyde, have a sporicidal and fungicidal activity.

4. Oxidizing agents:
These chemicals act by oxidizing the cell membrane of microorganisms, which results in loss of structure and leads to cell lysis. Some examples of disinfectants are:

5. Phenolics
They are the active ingredient of a household disinfectant and antiseptics, mouthwashes, handwashes and soaps.

6. Quaternary ammonium compounds
Quaternary ammonium compounds in combination with alcohol solution are used to kill non-enveloped virus such as norovirus, rotavirus, or poliovirus. Some low-alcohol formulations exhibit high efficacy against bacteria, enveloped viruses, pathogenic fungi, and mycobacteria.

7. Silver
Silver has antimicrobial properties but because of its limited shelf-life and unstability as disinfectant some chelated forms of silver such as Silver dihydrogen citrate (SDC), are used.

8. Copper alloy surfaces
Copper alloy surfaces have the ability to destroy a broad range of microorganisms and reduce bacterial contamination to 99.9% within 2 hours

9. Thymol-based disinfectant
Thymol is a phenolic chemical obtained from thyme and is considered as intermediate level of disinfectant.

10. Non-chemical Ultraviolet light is used for disinfecting smooth surfaces and also for municipal water treatment
Both antiseptics and disinfectants eliminate disease-causing organisms; antiseptics are applied to living skin or tissue to prevent infection, whereas disinfectants are applied to surfaces, equipment or other inanimate objects. Disinfectants are stronger and more toxic than antiseptics because they are applied to surfaces, not living tissue.Sterilization kills or removes all living organisms, including viruses, bacteria, and cells, from an object. Disinfection kills or removes disease-causing organisms, but not necessarily all organisms present on an object. Heat, radiation, filtration or chemical processes are used to sterilize objects such as medical instruments or surgical or laboratory equipment. If properly sealed, a sterilized object will remain sterile until the seal is broken. Sterilization is uncommon outside of hospital or laboratory settings. In most situations, disinfection is appropriate.