 There are a number of different classification systems for headaches.The most well-recognized is that of the International Headache Society.Causes of headaches may include dehydration, fatigue, sleep deprivation, stress, the effects of medications, the effects of recreational drugs, viral infections, loud noises, common colds, head injury, rapid ingestion of a very cold food or beverage, and dental or sinus issues (such as sinusitis).