The hypersensitivity reactions induced by drugs, some widely used, like central nervous system medication, can have various presentations. The lung is a frequent target for such events. We present the case of 40-year-old male patient, non-smoker, with infant encephalopaty, seizures since age of 6 with polimorphic crisis (mainly absences), with anticonvulsivant treatment since 2011 (carbamazepine, sodium valproate, levetiracetam), with no respiratory medical history. Current symptoms started two weeks before, with chest pain, dry cough. He received no antibiotics. Chest X-ray and thoracic CT scan (27 June 2013) showed a left pleral effusion. Left exploratory thoracocentesis extracted 20 ml reddish pleural fluid: eosinophilic exsudate (60%) with normal adenosin deaminase. He also presents moderate blood eosinophilia (13.7%-1780/mm3). Pulmonary infarction with secondary pleurisy, thoracic trauma, acute pancreatitis with secondary pleurisy were excluded. No Loeffler transient infiltrates were documented, serology for Toxocara is IgG positive (historical) and not significant for current episode, no symptoms suggestive for toxocarosis (characteristic to young children, patient had no liver enlargement etc.), no hidatidosis or trichinelosis were found. As an exclusion diagnosis, a hypersensitivity reaction to anticonvulsivant medication was considered (mentioned in literature) carbamazepine and sodium valproate (even if medication was taken for a longer time), with blood and pleural eosinophilia. Together with the neurologist, the mentioned drugs were stopped and he was started on lamotrigine 2 tb/day and levetiracetam 1 tb/day, well tolerated, no absences were noticed. Total remission of blood eosinophilia and partial remission of pleural effusion were noticed. Subsequent follow-ups confirm favourable evolution, with healing of pleurisy and normal blood cell count, which are stable at 7 months after changing anticonvulsivant treatment.