Examining essential oils

This article explores how the essential oils formulation came into being, what they can achieve in combination, and offers evidence to support their use in a mouthrinse.

It was in 1876 that Joseph Lister’s article exploring the use of antiseptics during surgery was first published, claiming that they could help to prevent infection when applied to wounds. He had tested several possible antiseptics, including oil of eucalyptus and thymol. This concept was taken further by Joseph Lawrence and Jordan Wheat Lambert, who created an antiseptic using four essential oils in 1879.  This formulation made use of Lister’s findings, combining the above-mentioned eucalyptus and thymol with menthol and methyl salicylate. This unique mix later formed the basis of LISTERINE®, named in acknowledgement of Lister’s important work in the field of antiseptics.3

When LISTERINE® first came into being, it had no specific use and, over the years, was used for a variety of purposes including cleaning floors and reducing dandruff, as well as, closer to today’s use, helping with halitosis.3

This was case until the 1970s, at which point the unique essential oil formulation was marketed as a mouthrinse to help prevent plaque.3 Today, the same four oils form the basis of the majority of LISTERINE® variants and, in combination, they have been shown to:

• Penetrate the plaque biofilm4

• Manage the bacterial load of the mouth5

• Reduce maturation of remaining biofilm colonies.6

Why use mouthwash?

Boyle and colleagues (2014) wrote: ‘Dental plaque is the main cause of oral diseases and can be removed mechanically by ‘effective’ brushing and flossing.’ However, they added that a considerable number of people leave a significant amount of plaque on their teeth despite brushing and interdental cleaning; in addition, soft tissues remain largely untouched.7

Offering a solution to this challenge, they continued that antimicrobial mouthrinses offer a considerable advantage when used as an adjunct to mechanical cleaning, as they, ‘[…] can reach virtually all residual plaque […]’.7

Working Group 2 at the 11th European Workshop in Periodontology on the primary prevention of periodontitis also saw value in the use of chemotherapeutic adjunct. They agreed that:

• ‘There is a universal recommendation to brush twice daily for at least 2 minutes with a fluoridated dentifrice. For periodontitis patients, 2 minutes is likely to be insufficient.

• ‘Daily interdental cleaning is strongly recommended to reduce plaque and gingival inflammation.’8 In addition, they suggested, for some patients, there are advantages to the adjunctive use of chemical agents for plaque control.8

The same year, Serrano and colleagues (2015) published a systematic review, investigating the clinical possibilities offered by adjunctive anti-plaque chemical agents. They established that, ‘The adjunctive use of chemical plaque control, together with mechanical control, offers advantages […] in plaque levels control.’9

Exploring formulations

It would seem, therefore, that there is a case to be made for the use of a mouthwash in some patients.7,8,9 Clearly, a number of mouthwash formulations are widely available, so what does the evidence suggest may offer the greatest benefit?

Boyle and colleagues (2014) examined the efficacy of chlorhexidine, cetylpyridinium (CPC), delmopinol, triclosan and essential oils in preventing dental plaque. They found that, over a period of less than three months, mouthwashes containing chlorhexidine were the most effective of the preparations considered, resulting in a reduction of dental plaque. When used for six months or longer, however, the essential oil mouthwash equalled or exceeded the effect of chlorhexidine in controlling plaque as an adjunct to standard care. It was also found that mouthwashes containing CPC or triclosan may also be effective, but less so than chlorhexidine and the essential oil-containing formulation. Lastly, mouthwashes containing delmopinol did not effectively control plaque.7

Araujo and colleagues (2015) also examined the adjunctive benefit of an essential oils mouthwash in relation to plaque. From their unique meta-analysis, they were able to demonstrate a clinically significant, site-specific benefit of a mouthrinse containing essential oils on plaque levels. 36.9% of participants who used mechanical methods and an essential oil-containing mouthrinse were found to have achieved at least 50% plaque-free sites in their mouths at 6 months, compared with only 5.5% of those who used mechanical cleaning alone.10

Bridging the oral health gap

The Adult Dental Health Survey (2009) indicated that two-thirds of the dentate adult population in England, Wales and Northern Ireland had visible plaque on at least one tooth. This is despite the fact that 75% of respondents said they brushed their teeth at least twice a day and, of those, 25% claimed to use dental floss.11

Given the proven ability of thymol, eucalyptol, menthol and methyl salicylate – the essential oils – to penetrate deep into the plaque biofilm, there are statistically significant greater odds of patients who add an essential oil mouthrinse to their daily mechanical cleaning regimen achieving a ‘[…] cleaner […] mouth, which may lead to prevention of disease progression.’10


  1. Lister J. On the antiseptic principle in the practice of surgery. BMJ 1867; 2(351): 246-248
  2. Cope Z. Joseph Lister, 1827-1912. BMJ 1967; 2(5543): 7-8
  3. Fine DH. Listerine: past, present and future – a test of thyme. Journal of Dentistry 2010; 38: S1-S5
  4. Pan et al. Determination of the in situ bactericidal activity of an essential oil mouthrinse using a vital stain method. J Clin Periodontol 2000; 27: 256-261
  5. Minah et al. Effects of 6 months use of an antiseptic mouthrinse on supragingival dental plaque microflora. J Clin Periodontol. 1989; 16: 347-352
  6. Johnson & Johnson. Data on file (2)
  7. Boyle et al. Mouthwash use and the prevention of plaque, gingivitis and caries. Head & Neck Oral Diseases 2014; 20(1): 1-76
  8. Chapple ILC et al. Primary prevention of periodontitis: managing gingivitis. J Clin Periodontol 2015; 42 (Suppl.16): S71-S76
  9. Serrano J et al. Efficacy of adjunctive anti-plaque chemical agents in managing gingivitis: a systematic review and meta-analysis. J Clin Periodontol 2015; 42 (Suppl. 16): S106-S138
  10. Araujo MWB et al. Meta-analysis of the effect of an essential oil–containing mouthrinse on gingivitis and plaque. JADA 2015; 146(8): 610-622
  11. Adult Dental Health Survey (2009). The Health and Social Care Information Centre 2011