What is 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.

• Halitosis (bad breath)
• Radiotherapy-induced mucositis
• Recurrent aphthous ulcers
• Oral lichen planus
• Acute mucositis associated with Stevens-Johnson syndrome / toxic epidermal necrolysis, or with erythema multiforme major
• After oral surgery
• As an adjuvant to toothbrushing to control bacterial plaque
• Adjuvant therapy for acute gingivitis and necrotising periodontitis.

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 solution – antimicrobial
• Cetylpyridinium chloride — antimicrobial
• Triclosan — anti-inflammatory, antimicrobial
• Sodium hypochlorite (dilute chlorine bleach) — antimicrobial
• Hydrogen peroxide — antimicrobial, 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:

• Local irritation
• Allergic or hypersensitivity reactions, including contact stomatitis, urticaria and (rarely) anaphylaxis.

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 to 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.