Eugenol allergy mimicking burning mouth syndrome.

Abstract

We report a patient with burning mouth syndrome resulting from allergic contact stomatitis caused by eugenol (found in condiments and dental mouthwash) and aggravated by lingua plicata. A 68-year-old woman was referred to the Department of Dermatology for investigation of lingua plicata and burning mouth syndrome for 2 years. Six months prior to the onset of her symptoms, she had a new prosthesis implanted in the upper jaw. She was screened for deficiency conditions, autoimmune disease, and infections, such as with Candida spp. and herpes simplex virus, without any abnormal findings. As contact stomatitis caused by dental materials or oral hygiene products was initially suspected, patch testing was performed with the European baseline series (including cobalt chloride), supplemented with a dental series, the mouthwash used by the patient “as is”, and constituents of the products that she had been using, including sodium benzoate (in the toothpaste) and eugenol (in the mouthwash). Testing was performed with the TRUE Test panel 1-3 (SmartPractice Mekos, Hillerød, Denmark), supplemented with the additional allergens in Finn Chambers on Scanpor tape (SmartPractice, Phoenix, Arizona), with an exposure time of 2 days. Readings were performed on day (D) 3 and D7, according to published guidelines.1 The patient reacted only to the mouthwash and eugenol 2% pet. with + reactions (but, interestingly, not to fragrance mix I), suggesting contact allergy to eugenol. This was consistent with the original suspicion. When the test results were discussed with the patient, addressing potential exposures to eugenol besides that in her mouthwash, she reported that, every morning, she ate yogurt sprinkled with cinnamon, and that she chewed cloves (Syzygium aromaticum) to freshen her breath during the day. Lingua plicata, also known as fissured tongue, is a benign idiopathic condition that may increase sensitivity to oral irritants and probably allergens.2 Eugenol is found in spices such as cinnamon and cloves,3 and is commonly used in dentistry as an analgesic and antimicrobial agent.4 Eugenol is also a commonly used fragrance component.5 In this case, eugenol was found in the patient's mouthwash and, quite surprisingly, also constituted a daily part of her diet. Burning sensations orally and contact allergy to eugenol are well known.6-8 In the present case, the bulk of eugenol exposure was from eating cinnamon every morning and chewing cloves during the day, as the mouthwash was not used on a daily basis. The patient was told to avoid all identified exposures. At follow-up after 8 weeks, the burning sensation was significantly reduced, whereas the lingua plicata remained. Burning mouth syndrome is still a poorly understood diagnosis of exclusion9; in this case, the patient actually suffered from contact allergy to eugenol in the spices that she ingested in vast amounts. The authors declare no potential conflict of interests.