Drug reactions refer to the unintended effects that can occur when a person takes medication. These reactions can range from mild side effects, like nausea or dizziness, to severe allergic responses, such as difficulty breathing or swelling. Understanding these reactions is crucial for safe medication use. There are two main types of drug reactions: adverse drug reactions and allergic drug reactions. Adverse reactions are harmful effects that occur at normal doses, while allergic reactions happen when the immune system mistakenly identifies a drug as harmful. Monitoring and reporting these reactions can help improve patient safety and treatment outcomes.