An allergic drug reaction occurs when the immune system mistakenly identifies a medication as a harmful substance. This can lead to various symptoms, such as rashes, itching, swelling, or difficulty breathing. Common medications that may cause allergic reactions include penicillin, aspirin, and certain antibiotics. The severity of allergic drug reactions can vary from mild to life-threatening. In some cases, they can trigger anaphylaxis, a severe reaction that requires immediate medical attention. It is important for individuals to inform their healthcare providers about any known allergies to medications to prevent adverse reactions in the future.