Author: Dr Shaochen Liu, Dermatology Registrar, Greenlane Hospital, Auckland, New Zealand; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, February 2016.

What is a mouthwash?

A mouthwash is a solution used to rinse the oral cavity. This may be to maintain oral hygiene, to prevent dental plaque, or for symptomatic relief.

A mouthwash is sometimes called a mouth rinse.

Who needs a mouthwash?

A mouthwash may be used short-term for a variety of conditions. Some examples follow.

A fluoride-containing mouthwash may be used to reduce the risk of cavities / dental caries.

What do mouthwashes contain?

Mouthwashes contain a variety of ingredients. The active ingredients include:

  • Chlorhexidine gluconate – antimicrobial
  • Povidone-iodine – antimicrobial
  • Benzydamine hydrochloride – anti-inflammatory, analgesic, antimicrobial
  • Essential oils, such as eucalyptol, menthol, methyl salicylate and thymol. These are often formulated in an alcohol-based solutionantimicrobial
  • Cetylpyridinium chloride – antimicrobial
  • Triclosan – anti-inflammatory, antimicrobial
  • Sodium hypochlorite (dilute chlorine bleach) – antimicrobial
  • Hydrogen peroxideantimicrobial, bleach
  • Anti-bacterial peroxidase enzymes, such as lysozyme, lactoferrin, glucose oxidase, lactoperoxidase – antimicrobial
  • Fluoride – remineraliser, antimicrobial
  • Sodium bicarbonate – alkaliniser

How do mouthwashes work?

The active ingredients in mouthwashes act in several ways.

  • Antimicrobials kill bacteria, reducing plaque and halitosis.
  • Anti-inflammatories decrease pro-inflammatory cytokines, reducing pain.
  • Fluoride (fluorapatite, fluoro-hydroxyapatite) re-mineralises tooth enamel, enhancing resistance to acid and preventing cavity/caries formation.
  • Bicarbonate alkalinises salivary pH. It reduces the erosive effect of acid produced by oral bacteria, and promotes enamel mineralisation, especially in people with dental caries.

How to use a mouthwash

Mouthwash is typically used twice-daily, as a short-term adjuvant to toothbrushing.

  • Depending on the type and concentration, mouthwash may require dilution prior to use.
  • Typically, 15–20 mL of solution is used.
  • Empty the mouthwash into the mouth, swill it around vigorously, and gargle for at least 30 seconds.
  • Spit out the mouthwash completely; do not swallow it.

What are the adverse effects of mouthwash?

The adverse effects of mouthwash depend on its ingredients, and include:

Adverse effects of chlorhexidine make it unsuitable for long-term use:

  • Unpleasant or altered taste
  • Burning sensation
  • Desquamation and irritation of the oral mucosa
  • Discolouration of soft tissues, teeth and restorations
  • Supragingival calculus deposition
  • Parotid swelling

Benzydamine has local anaesthetic and analgesic properties. It can cause:

  • Numbness or tingling in the oral cavity
  • Dry mouth

Ethanol associated side-effects may occur with mouthwashes containing essential oils.

  • Mucosal irritation and dryness
  • Oral pain, with intensity proportional to the concentration of ethanol
  • Mouthwashes with > 20% ethanol risk keratosis, epithelial detachment, mucosal ulceration, gingivitis and petechiae.

Other reported adverse effects follow

  • Cetylpyridinium chloride may cause extrinsic tooth stains.
  • Triclosan has been reported to cause desquamation.
  • Sodium hypochlorite has a ‘bleach taste’ and may cause extrinsic brown tooth stains and a burning sensation.
  • Hydrogen peroxide can cause oral dryness, taste disturbance, diffuse mucosal whitening and elongation of the filiform papillae (hair-like structures on the surface of the tongue).
  • Anti-bacterial peroxidases tend to be acidic, with a pH of around 5.15, increasing the potential for dental erosion, especially with long-term use.

Contraindications and precautions

  • Mouthwashes are contraindicated in those who have allergic or hypersensitivity reactions to an ingredient.
  • They are contraindicated in children under six years of age, due the risk of swallowing the mouthwash.
  • Iodine-containing mouthwash is not recommended for people with hyperthyroidism or other thyroid diseases, due to possible systemic absorption of iodine.
  • Long-term use of mouthwash is not recommended.
  • The association between long-term use of alcohol-containing mouthwash and increased risk of oral cancer is controversial.


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