The most common triggers of anaphylactoid reactions are Iodinated radiopaque contrast agents Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) Opioids Monoclonal antibodies Exercise Symptoms and Signs of Anaphylaxis Symptoms of anaphylaxis typically begin within 15 minutes of exposure and involve the skin, upper or lower airways, cardiovascular system, and / or gastrointestinal (GI) tract.