Sublingual immunotherapy for cedar pollinosis possibly triggers eosinophilic esophagitis

Sublingual immunotherapy (SLIT) is an effective and popular treatment for cedar pollinosis. Although SLIT can cause allergic side effects, eosinophilic esophagitis (EoE) is a lesser-known side effect of SLIT. A 26-year-old male with cedar pollinosis, wheat-dependent exercise-induced anaphylaxis, and food allergies to bananas and avocados presented with persistent throat itching, difficulty swallowing, heartburn, and anterior chest pain 8 days after starting SLIT for cedar pollinosis. Laboratory examination showed remarkably elevated eosinophils, and esophagogastroduodenoscopy revealed linear furrows in the entire esophagus. Histological examination of an esophageal biopsy specimen revealed high eosinophil levels. The patient was strongly suspected with EoE triggered by SLIT. The patient was advised to switch from the swallow to the spit method for SLIT, and the symptoms associated with SLIT-triggered EoE were reduced after switching to the spit method. This case highlights the importance of recognizing SLIT-triggered EoE as a potential side effect of SLIT for cedar pollinosis, especially with the increasing use of SLIT in clinical practice. EoE can occur within a month after initiating SLIT in patients with multiple allergic conditions, as observed in our case. Furthermore, the spit method should be recommended for patients who experience SLIT-triggered EoE before discontinuing SLIT.