Understanding the difference helps you respond quickly and safely. An allergic reaction is immune-mediated—the body’s immune system reacts to the drug, often with symptoms like hives, swelling, wheezing, or even anaphylaxis. An adverse drug reaction covers any harmful effect from a drug, which may or may not involve the immune system; these can be dose-related side effects (like nausea or constipation) or idiosyncratic reactions that aren’t immune-driven. Because allergic reactions can be life-threatening, the appropriate response when symptoms are severe is to stop the drug immediately, notify the nurse, and document what happened so the care team can take the next steps. For adverse drug reactions, the approach depends on severity, but stopping the drug and reporting are part of safe practice when the reaction is serious. In short, immune involvement defines an allergic reaction, while ADRs include a broader range of harmful effects; severe reactions require stopping the drug, escalation, and thorough documentation.