Analgesic
Analgesics are pain relievers and also offset the symptoms of colds and flu. The most common are paracetamol, aspirin and ibuprofen. These are available 'over the counter' and generally considered safe if used as directed. They can be taken alone or as an ingredient of a "cold relief medicine. Note the pain or discomfort that you are trying to treat with an analgesic (e.g. headache, sore throat, etc.) may be the symptom of some illness that requires additional medical attention.
Anti-histamines
Anti-histamines are used in many "over the counter drugs such as cold cures and the treatment of allergies such as hay fever. The side effects include drowsiness and dizziness; therefore, medicines containing anti histamines are unacceptable when flying. In a number of fatal accidents in recent years, traces of antihistamines and other 'over the counter medications have been found during the post-mortem of the pilot.