A pain reliever is a medication or substance that helps to reduce, alleviate or eliminate pain. It can be an over-the-counter drug such as ibuprofen or aspirin, or it may require a prescription from a doctor, depending on the severity and duration of the pain being experienced. Pain relievers work by reducing inflammation, inhibiting the production of prostaglandins, or blocking the transmission of nerve impulses that cause pain. They can be taken orally, applied topically, or administered through injection, depending on the specific medication and the type of pain being treated.