The most common symptom of cluster headaches is severe, constant, pain behind one eye. Symptoms generally last for an hour or two and then resolve without treatment. Headaches occur in clusters, over several days in a row.

Characteristics of the headaches include:

• Intense and steady pain
• Boring or searing pain
• Usually located behind one eye
• Begins within 2-3 hours of falling asleep

Additional symptoms tend to occur on the same side as the headache pain.

Additional symptoms of cluster headaches include:

• Small pupil
• Drooping eyelid
• Facial flushing
• Facial swelling
• Eye tearing
• Runny nose