A cluster headache begins as a severe, sudden headache. The headache most commonly strikes 2 to 3 hours after falling asleep, usually during the dreaming (rapid eye movement, or REM) phase. However, the headache may occur while you are awake. The headache tends to occur at the same time of day.

The pain occurs on one side of the head. It may be described as:

• Burning
• Sharp
• Steady

The pain may occur in, behind, and around one eye. It may:

• Involve one side of the face from neck to temples
• Quickly gets worse, peaking within 5 to 10 minutes

The strongest pain may last 30 minutes to 2 hours.

The eye and nose on the same side of the head pain may also be affected. Symptoms can include:

• Swelling under or around the eye (may affect both eyes)
• Excessive tearing
• Red eye
• Rhinorrhea (runny nose) or one-sided stuffy nose (same side as the head pain)
• Red, flushed face

Cluster headaches may occur daily for months, alternating with periods without headaches (episodic), or they can recur for a year or more without stopping (chronic).

Your health care provider can diagnosis this type of headache by performing a physical exam and asking questions about your symptoms and medical history.

If a physical exam is done during an attack, the exam will usually reveal Horner syndrome (one-sided eyelid drooping or a small pupil). These symptoms will not be present at other times. No other neurological changes will be seen.

Tests, such as an MRI of the head, may be needed to rule out other causes for the headaches.