(HealthDay News) -- Cluster headaches are severe headaches that usually cause pain behind or around one eye. The nose may also be red, swollen or runny on the same side as the headache.
These headaches do not run in families and do not appear to be related to other conditions, the American Academy of Family Physicians says.
The academy says the following factors may trigger cluster headaches:
- Certain medications, including nitroglycerin.
- Frequent smoking.
- Changes in sleep schedule.
- An abnormality in the hypothalamus, the part of the brain that controls the body's "biological clock."
