Pain is part of the body's natural response to infection or injury; it lets us know something is wrong. Pain is usually the result of inflammation somewhere in the body. There are many different types of pain relief; different in how they are given (e.g. gels, sprays, tablets) and different in how strong they are. Mild to moderate pain can be treated with paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin or ibuprofen. Severe pain is usually treated with an opioid painkiller such as tramadol, morphine or fentanyl. Opioid painkillers work best when used for short periods of time only. Long-term use of opioid painkillers can result in tolerance and dependence on the medicine. Nerve pain can be harder to treat and medicines such as pregabalin and gabapentin are usually tried first.