• Swelling under or around the eyes (usually one eye, on the same side as the head pain)
• Excessive tears (on the affected side)
• Red eye (on the affected side)
• Rhinorrhea (runny nose) or nasal congestion (typically occurs on only one side of the nose, the same side as the head pain)
• Red, flushed face
• Headache
  • Begins suddenly
  • Commonly begins 2 to 3 hours after falling asleep
  • Steady
  • Sharp
  • Burning or boring pain
  • Characteristically occurs on one side of the head
  • May occur in and around one eye
  • May involve one side of the face from neck to temples
  • Pain quickly gets worse, peaking within 5 to 10 minutes
  • Peak pain may last one-half to 2 hours

Cluster headaches may be diagnosed by your health care provider based on the symptoms and a physical examination. Tests may be required to rule out other causes of the symptoms. Examination usually shows no specific neurologic effects except for Horner's syndrome (one-sided eyelid drooping or small pupil) during an attack that is not present between episodes. (This can evolve into persistent Horner's syndrome.)

An MRI of the head may be done to rule out other pathology.