The natural course of idiopathic pulmonary fibrosis (IPF) is unpredictable at the time of diagnosis. Some patients may experience episodes of acute respiratory worsening that have been termed acute exacerbations. A 58-year-old male was admitted to our Emergency Department due to progressive and intense dyspnea and dry cough after accidental inhalation of waterproof’s vapor containing siloxanes. Chest high resolution computed tomography (HRCT) scan showed diffuse and bilateral ground glass attenuation, basal predominant reticular abnormalities and subpleural honeycombing. The patient didn’t know that he suffered from IPF and siloxanes’ inhalation triggered an acute exacerbation of his disease. Clinical course after the inhalation was aggressive and, despite steroids and cyclophosphamide therapy, the patient died 3 months after due to a respiratory failure. Inhalation of water repellents has been associated with an acute onset of respiratory symptoms and acute lung injury; usually, however, the prognosis is commonly good with a complete recovery. Our case is an example of an extremely negative reaction probably because of pre-existing and misdiagnosed IPF. Currently, no literature concerning water repellent inhalation as a trigger of acute exacerbation of IPF is available.