Cluster headaches are a series of relatively short but extremely painful headaches every day for weeks or months at a time. You tend to get them at the same time each year, such as the spring or fall. Because of their seasonal nature, people often mistake cluster headaches for symptoms of allergies or business stress.

We don't know what causes them, but we do know that a nerve in your face is involved, creating intense pain around one of your eyes. It's so bad that most people can't sit still and will often pace during an attack. Cluster headaches can be more severe than a migraine, but they usually don't last as long.

These are the least common type of headaches, affecting less than 1 in 1,000 people. Men get them more than women do. You usually start getting them before age 30. Cluster headaches may disappear completely (go into remission) for months or years, but they can come back without any warning.