What is an antiseptic?
An antiseptic is a chemical agent that slows or stops the growth of micro-organisms on external surfaces of the body and helps to prevent infections. Antiseptics should be distinguished from antibiotics that destroy micro-organisms inside the body, and from disinfectants, which destroy micro-organisms found on inanimate (non-living) objects. However, antiseptics are often referred to as skin disinfectants.
Most chemical agents can be used as both an antiseptic and a disinfectant. The purpose for which it is used is determined by its concentration. For example, hydrogen peroxide 6% solution is used for cleansing wounds, while stronger solutions (> 30%) are used in industry as bleach and oxidising agent.
Types of antiseptic
Antiseptics can be classified according to their chemical structure. Commonly used antiseptic groups include alcohols, quaternary ammonium compounds, chlorhexidine and other diguanides, antibacterial dyes, chlorine and hypochlorites, inorganic iodine compounds, metals, peroxides and permanganates, halogenated phenol derivatives and quinolone derivatives. The following table lists some of the agents within these groups.
- Ethyl alcohol 70%
- Isopropyl alcohol 70%
- Used as a skin disinfectant
Quaternary ammonium compound
- Benzalkonium chloride
- Methylbenzethonium chloride
- Benzethonium chloride
- Cetalkonium chloride
- Cetylpyridinium chloride
- Dofanium chloride
- Domiphen bromide
- Used as skin disinfectant, irrigation, and to preserve eye drops
Chlorhexidine and other diguanide
- Chlorhexidine gluconate
- Chlorhexidine acetate
- Used as pre-operative skin disinfectant, to treat wounds, and for bladder irrigation
- Proflavine hemisulphate
- Brilliant green
- Crystal violet
- Gentian violet
- Used as a skin disinfectant and to treat a wound or burn
Peroxide and permanganate
- Hydrogen peroxide solution
- Potassium permanganate solution
- Benzoyl peroxide
- Used as wound cleanser, gargle and mouthwash, for irrigation and as a skin disinfectant
Halogenated phenol derivative
- Hexachlorophane/hexachlorophene (no longer available)
- Used as a skin disinfectant and in medicated soap and solution
- Hydroxyquinoline sulphate
- Potassium hydroxyquinoline sulphate
- Dequalinium chloride
- Used to treat wounds, in throat lozenges and as a skin disinfectant
- Burow's solution (aqueous solution of aluminium acetate)
- Bleach baths
Uses of antiseptic
Antiseptic is mainly used to reduce levels of microorganisms on the skin and mucous membranes. The skin and mucous membranes of the mouth, nose, and vagina are home to a large number of micro-organisms (which are normally harmless).
- When the skin or mucous membranes are damaged or breached in surgery, antiseptic is used to disinfect the area and reduce the chances of infection.
- People who are treating patients with wounds or burns should wash their hands with an antiseptic solution to minimise the risk of cross infection.
Antiseptics are used for:
- Handwashing — chlorhexidine gluconate and povidone-iodine solutions are often used in hand scrubs and hand rubs in hospital settings. Alcohol in concentrations > 60% will destroy pathogens such as the SARS-CoV-19 virus.
- Pre-operative skin disinfection — antiseptics applied to the operation site to reduce the resident skin flora. Caution should be used in facial use of solutions containing chlorhexidine, as these can injure the eye causing keratitis.
- Mucous membrane disinfection — antiseptic irrigations may be instilled into the bladder, urethra or vagina to treat infections or cleanse the cavity prior to catheterisation.
- Preventing and treating infected wounds and burns — antiseptic preparations are available over-the-counter from your pharmacist to treat minor cuts, abrasions and burns.
- Treating mouth and throat infections — dequalinium chloride has both antibacterial and antifungal properties and is the active ingredient in antiseptic throat lozenges.
Are antiseptics effective and safe?
The effectiveness and complete safety of antiseptics have proved to be quite difficult to establish.
Due to concern about the potential for systemic absorption, in December 2017, the US Food and Drug Administration (FDA) ruled that 24 ingredients — including triclosan —used in non-prescription (over-the-counter) antiseptic products (such as hand washes, hand scrubs/rubs and patient antiseptic preparations) intended for use by health care professionals in a hospital setting or other health care situations outside the hospital, are generally not recognised as safe and effective (often due to inadequate data). The 24 ingredients will be classified as new drugs requiring regulatory approval for marketing from December 2018. A decision was deferred on a further six ingredients (benzalkonium chloride, benzethonium chloride, chloroxylenol, alcohol, isopropyl alcohol, and povidone-iodine).
Precautions when using antiseptic
Strong antiseptic should be diluted before it is applied to the skin, as concentrated products including chlorhexidine may cause chemical burns or severe irritant contact dermatitis. Prolonged contact with dilute antiseptic can also cause erosive contact dermatitis, as described with chlorhexidine-impregnated dressings.
Antiseptic bought from the pharmacy should not be used for more than one week. Stop using the antiseptic and see a doctor if:
- The affected area has not healed or improved.
- There is a large wound, deep cut, large burn, or abrasion embedded with particles that won’t wash away
- Injury is due to a human bite or animal bite
- An eye is injured.
Do not use antiseptics to treat sunburn or deep skin infection. Remember that antiseptic only reduces microorganisms on the surface of the tissue and that antibiotics will be needed to treat infection within the tissues.
People with allergies of any kind should check with a doctor or pharmacist before using an over-the-counter antiseptic product. Some antiseptics can irritate the skin and cause allergic contact dermatitis. Chlorhexidine has been reported to rarely cause anaphylaxis.
What about antibacterial soap?
In September 2016, the US Food & Drug Administration (FDA) issued a final rule establishing that over-the-counter (OTC) consumer antiseptic wash products containing certain active ingredients can no longer be marketed. Nineteen of these are listed, including triclosan and triclocarban. Regulators in other countries may follow with similar rulings. Reasons include:
- There is no scientific evidence that antibacterial wash is any better than soap and water in preventing the spread of germs
- Household use of antibacterial ingredients may do more harm than good over the long-term, such as promoting bacterial resistance (see MRSA).
Hand sanitiser containing at least 60% alcohol can be used, if soap and water are not available. Emollients are recommended after use if the hands are dry or develop contact dermatitis due to the use of antiseptics.
If you are not based in New Zealand, we suggest you refer to your national drug approval agency for further information about medicines (eg, the Australian Therapeutic Goods Administration and the US Food and Drug Administration) or a national or state-approved formulary (eg, the New Zealand Formulary and New Zealand Formulary for Children and the British National Formulary and British National Formulary for Children).