Headache itself is a painful and often disabling feature of a relatively small number of primary headache disorders. It also occurs secondarily to a considerable number of other conditions. A wide range of headache types have been classified in detail by the International Headache Society The most common among them – tension-type headache (TTH), migraine, cluster headache and the so-called chronic daily headache syndromes – cause substantial levels of disability. Headache has been and continues to be underestimated in scope and scale, and headache disorders remain under-recognized and under-treated throughout the world.

Headache disorders are among the most common disorders of the nervous system. Primary headache disorders, such as migraine, tension-type headache, cluster headache, and the so-called chronic daily headache syndrome, can cause substantial levels of disability. Headache can also occur as a symptom of a considerable number of other conditions. There are effective treatments for all types of headache.

A number of diagnostic schemata for headache have been proposed. As early as 1962, for example, the Ad Hoc Committee on Classification of Headache listed the features that are typically present during certain types of headache, but it failed to indicate which features or combinations of features were required to establish a diagnosis.

Headache disorders cause more than 1 percent of all disability and 9 percent of all lost labor in the US every year. By 1988, recognizing the need for improvement in headache classification, the International Headache Society (IHS) published a new system.

Treatment of an uncomplicated headache is usually symptomatic with over-the-counter painkillers such as aspirin, paracetamol (acetaminophen), or ibuprofen, although some specific forms of headaches (e.g., migraines) may demand other, more suitable treatment. It may be possible to relate the occurrence of a headache to other particular triggers (such as stress or particular foods), which can then be avoided.

ACHE is an acronym for the American Headache Society (AHS) Committee for Headache Education. ACHE is sponsored and directed by AHS which is a professional society of health care providers dedicated to the study and treatment of headache and face pain. Founded in 1959, AHS brings together physicians and other health providers from various fields and specialties to share concepts and developments about headache and related conditions.