The purpose of this research study is to learn new information about the underlying cause of aspirin-exacerbated respiratory disease (AERD) and the benefit of high-dose aspirin therapy. AERD is a disease that involves asthma, recurring nasal polyps, and respiratory reactions to aspirin and other nonsteroidal anti-inflammatory drugs. This study will be conducted on individuals with AERD who are referred to the Brigham and Women's Hospital AERD Center for clinical evaluation and potential aspirin desensitization. Desensitization to aspirin and subsequent treatment with daily high-dose oral aspirin is standard of care for patients with AERD who do not respond adequately to steroids and have recurrent nasal polyposis or symptomatic asthma. This study will involve four visits to Brigham and Women's Hospital and will align closely with the standard of care for the treatment of AERD.