Acid anhydrides, such as phthalic anhydride (PA) or trimellitic anhydride, are low molecular weight reactive chemicals that has been widely used in the manufacture of plastics and paints. They have been reported to cause rhinitis, dermatitis, asthma, and hemorrhagic alveolitis. These adverse effects are a result of direct irritation to the mucosa or its ability to cause immune reaction. We report a 32-year-old man with PA induced asthma, confirmed by specific inhalation challenge. He complained of recurrent chest tightness, sneezing, and dyspnea while at work. These symptoms develop 3 years after exposure to this chemical. Inhalation challenge with PA fume reproduced his symptoms and demonstrated an early asthmatic response. Specific IgE antibody against to PA was elevated.