What happens if people start drinking mouthwash as surrogate alcohol? A quantitative risk assessment
Graphical abstract
Highlights
► Mouthwash may be ingested as surrogate alcohol when other alcoholic beverages are unavailable. ► Besides alcohol (ethanol), mouthwashes regularly contain benzoic acid, methyl salicylate, thymol, eucalyptol and menthol. ► Acceptable daily intake levels of these compounds may be exceeded in heavy and dependent drinking scenarios. ► Besides ethanol, methyl salicylate and thymol were found to have the lowest margin of exposure. ► The alcoholic strength of mouthwashes should be labeled.
Introduction
In the context of surrogate alcohol consumption, the possibility of ingestion of mouthwashes (i.e. cosmetic or medicinal products intended for oral rinsing) was regularly pointed out in the past (Lachenmeier et al., 2007). The products preferred as substitute for alcohol contain typically between 10% and 30% vol of alcohol (ethanol) with the most common products being between 20% and 27% vol, which is higher than the strength of beer or wine (Armenta et al., 2006, Egbert et al., 1985, Gagari and Kabani, 1995, Haq et al., 2009, Khan et al., 1999, Lachenmeier et al., 2008, Lachenmeier et al., 2009a, Massey and Shulman, 2006, McCullough and Farah, 2008, O’Reilly et al., 1994). The acute toxicity of mouthwash exposure appears to be rather low and only few cases of fatal intoxications due to intentional ingestion of very large amounts (up to 3 L) in adults were reported (Soo Hoo et al., 2003, Sperry and Pfalzgraf, 1990). The accidental ingestion by children may also be a problem (e.g., see Massey and Shulman (2006) for review) but this has been ameliorated since the mandatory introduction of child-resistant closures (Mrvos and Krenzelok, 2007).
The major problem and open question concerns a potential intentional long-term or chronic exposure to mouthwash. The American Association of Poison Control Centers reported 3547 cases of adult ethanol-containing mouthwash exposure for 2010 (Bronstein et al., 2011). Surveys of hospitalized alcohol-dependent patients have shown that mouthwash was the preferred product of all types of unrecorded alcohol (Egbert et al., 1985, Egbert et al., 1986). In addition to the low price, the major reason reported as rationale for drinking this type of surrogate alcohol were the ready availability in settings where alcoholic beverages are otherwise unavailable such as in hospitals, prisons, nursing homes, or in military settings (Egbert et al., 1985, Egbert et al., 1986, Khan et al., 1999, McLay et al., 2009, Westermeyer and Terpolilli, 2001). Some case reports have shown that mouthwash may constitute the single form of alcohol intake over long periods up to years (Egbert et al., 1985, Soo Hoo et al., 2003, Westermeyer and Terpolilli, 2001). There is no general consensus in the literature regarding the chronic toxicity of mouthwash ingestion. Some authors suggest that the effects are purely caused by ethanol and similar to intake of the same doses of any alcoholic beverage (Egbert et al., 1985, Sperry and Pfalzgraf, 1990). The fact that mouthwashes are intended for intraoral (but not ingestion) purposes was stated as reason because this does limit the amount, type and quantity of denaturant that can be utilized without compromising the product’s safety (Sperry and Pfalzgraf, 1990). In fact this appears to restrict the usage of methanol as denaturant, and most likely a flavour compound such as thymol or methyl salicylate may be used to denature the alcohol instead (Andersen, 2008, Lachenmeier et al., 2007). However, these compounds and other ingredients of mouthwash were postulated to have health effects above the effects of ethanol. For example, the profound anion-gap metabolic acidosis and osmolar gap following massive mouthwash ingestion (3 L) were judged to be caused by non-alcoholic ingredients (eucalyptol, menthol, and thymol) (Soo Hoo et al., 2003). A similar finding of severe metabolic acidosis (2–3 L mouthwash ingestion) that could not be fully attributed to ethanol metabolism was reported by Westermeyer and Terpolilli (2001). Apart from these extreme cases, the literature review did not reveal any adverse effect of mouthwash ingredients for moderate or even heavy users. As we have observed and are concerned about the practice of mouthwash ingestion in Canada, this study intends to quantitatively assess the risk for consumers of this surrogate alcohol. As the International Nomenclature of Cosmetics Ingredients (INCI) labeling does not contain quantitative information about all compounds, we have conducted chemical analysis of 30 mouthwashes and use these result to estimate the margin of exposure.
Section snippets
Samples and analytical procedure
A convenience sampling was conducted in markets of the affiliated institutions. Samples consisted of ready-to-use alcohol-containing mouthwashes, mouth rinses and oral rinses available without prescription on the German (n = 14) and Canadian (n = 16) market. The samples were purchased in supermarkets, drug stores and pharmacies. The samples were selected on the basis of what alcohol-dependent people would select as surrogate alcohol (the highest possible alcoholic strength for the lowest possible
Results
Detailed analytical results for all 30 analyzed samples are listed in the supporting information and a summary is provided in Table 1. Most of the investigated brands have the following ingredients: alcohol (100% of all samples), benzoic acid (or its salts) (87%), and methyl salicylate (67%). Most products also contain monoterpenoid flavour compounds such as thymol (30%), eucalyptol (90%) and menthol (93%). We also detected a high incidence of the artificial sweetener sodium saccharin (97%),
Discussion
This discussion will mainly focus on moderate and short-term heavy use (about 4 standard drinks in the form of mouthwash), e.g. in settings where other alcoholic beverages are unavailable, which according to the evidence presented in the introduction appears to be more common than the long-term dependent use.
The risk associated with ingestion of mouthwash appears to be threefold:
- 1.
Adverse effects associated with the intended use such as allergic reactions to some of the constituents (Gagari and
Conclusions
The major conclusion is that the occasional or even chronic ingestion of mouthwash would not cause health effects above the effects of ethanol alone. Only in extreme exposures for alcohol dependent consumers (several bottles at one occasion), ingredients such as thymol or methyl salicylate could exacerbate the effects of ethanol, especially by contributing to metabolic acidosis. Risk management communications for this consumer group should clearly advise against mouthwash consumptions as well
Conflict of Interest
The authors declare that there are no conflicts of interest.
Acknowledgements
The authors thank Julie Grayson for English copy-editing of the manuscript. The research leading to these results has been conducted in the context of establishing a methodology for comparative risk assessment using the margin of exposure approach for the European Community’s Seventh Framework Programme under Grant agreement n° 266813 - Addiction and Lifestyles in Contemporary Europe - Reframing Addictions Project (ALICE RAP). Participant organisations in ALICE RAP can be seen at
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