Headaches are classified as either primary or secondary, and primary headaches are caused by problems with the structures in the head that are sensitive to pain. Secondary headaches are caused by any one of a number of underlying medical conditions. In these cases, the medical condition generally causes some form of swelling that presses on the nerves in the head, triggering a headache.
Primary headaches are the most common type. Cluster headaches, migraines and tension headaches are all classified as primary headaches. Less common forms of primary headache include cough headaches, sex headaches, chronic daily headaches and exercise headaches. Stress, poor posture, alcohol consumption, lack of sleep and skipped meals have been linked to primary headaches in some people.
Dozens of different conditions cause secondary headaches. Spinal headaches occur when someone has a low level of cerebrospinal fluid, and sinus headaches are related to inflammation of the sinus cavities. Secondary headaches are also associated with stroke, concussion, glaucoma, influenza, meningitis and dental problems. Ice cream headaches are considered a type of secondary headache, since ice cream headaches occur when something cold touches the roof of the mouth, affecting some of the nerves that determine how much blood flows to the head. As a result, the blood vessels in the head swell, resulting in a headache that may last anywhere from one to five minutes.