inclusion criteria: - people familiar with the use of face masks, absence of allergy or intolerance to sodium saccharin or materials used, absence of relevant systemic diseases, age between 18-65 years, absence of obvious facial hair and signing the informed consent.

inclusion criteria: - people familiar with the use of face masks, absence of allergy or intolerance to sodium saccharin or materials used, absence of relevant systemic diseases, age between 18-65 years, absence of obvious facial hair and signing the informed consent.