They are called cluster headaches because the attacks come in groups. The pain arrives with little, if any, warning, and it has been described as the most severe and intense of any headache type. It generally lasts from 30 to 45 minutes, although it might persist for several hours before it disappears. Unfortunately, it can reoccur later in the day.
Most sufferers experience one to four headaches a day during a cluster period.
Clusters often occur during spring or autumn and, thus, are often incorrectly associated with allergies. Approximately 10 percent of the sufferers, however, experience chronic cluster headaches that occur all year long. It is estimated that less than one percent of the population are victims of cluster headaches, and they encounter the headache somewhere between the ages of 20 and 45. No warnings, no preliminary signs. A massive, killing pain came over my right eye.