A Malmö University researcher has found that using toothpastes without added flavours could help prevent against contact allergic reactions like eczema around the mouth and oral lesions.

Many commercial toothpastes contain carvone, a mint flavour used to give a fresh and pleasant aroma. Although carvone is a relatively mild allergen, it has been linked to adverse reactions in the oral mucosa. Researcher and PhD candidate Liv Kroona has been investigating the connection between carvone and the autoimmune illness oral lichen planus. 

“People allergic to carvone tend to have oral lichen planus, but we do not yet know whether this is purely due to their allergy or if it’s part of the broader clinical picture of the illness,” explains Kroona.

Kroona’s study explored the amount of carvone in 66 different toothpaste brands. While varying concentrations of the ingredient were found in all flavoured toothpastes, only some contained levels that could cause a contact allergic reaction.

In one of the sub-studies, study participants with a carvone contact allergy and oral lichen planus were required to use toothpaste that contained one per cent carvone for a full month.

“Several changes occurred and adverse effects were clearly observed among the patients. They experienced irritation in or around the mouth as well as reporting reduced quality of life. Choosing a toothpaste with no flavour is an effective way to reduce the discomfort caused by carvone for contact allergic individuals,” says Kroona.

A second sub-study compared tissue samples between individuals with a carvone allergy and those who only had oral lichen planus. Kroona found no great difference in the degree of inflammation or in the incidence of inflammatory cells between the two groups.

“Since both the clinical symptoms and the appearance in tissue samples are so similar, there’s a risk that carvone contact allergy is not being detected or being misdiagnosed. Avoiding mint flavoured toothpastes is certainly an easier and less costly treatment than being treated with coticosteroids," she says.

“Dentists who treat patients with mucosal diseases like oral lichen planus should be made aware that contact allergic reactions to flavours can have a detrimental effect on their patients.”

Read the study

Liv Kroona defended her thesis, Oral contact allergy to carvone – with a focus on oral lichen, on Friday, November 9 at the Faculty of Odontology. 

Find out more about Kroona's research