Cluster headaches are rare, debilitating attacks, according to the NHS.
The attacks tend to be in episodes, and can begin quickly, without warning.
Patients have described a cluster headache as a stabbing sensation behind the eye.
An attack can last anywhere between 15 minutes and three hours, but often appear at the same time of day or night.
“The pain is very severe and is often described as a sharp, burning or piercing sensation on one side of the head,” the NHS said.
“It’s often felt around the eye, temple and sometimes face. It tends to occur on the same side for each attack.
“People often feel restless and agitated during an attack because the pain is so intense, and they may react by rocking, pacing, or banging their head against the wall.”
About 125,000 people in the UK have cluster headaches. Men over the age of 20 are most likely to suffer from the condition.
Cluster headache symptoms tend to appear on one side of the face.
As well as the searing pain, it can also cause reddening of the eye, and the eyelid to become droopy.
Patients have described a feeling of pressure inside the ears, as well as a runny or blocked nostril and facial sweating.
The headaches could appear once every other day, or as much as eight times in one day.
While the exact cause of the condition isn’t fully understood, you could be more at risk of the condition if you’re a smoker, or have a family history of cluster headaches.
For patients, the attacks may be triggered by bright, flashing lights, alcohol, strong smells, or watching television.
“Avoiding the triggers of cluster headaches can help prevent them,” the NHS said. “For example, you should avoid drinking alcohol during a cluster headache bout.
“You should also try to avoid strong smelling chemicals, such as perfume, paint or petrol, which can often trigger an attack.
“Becoming overheated during exercise can also bring on a cluster headache attack in some people, so it’s best not to exercise during a bout.”
If you think you may be having a cluster headache, you should speak to your GP. Alternatively, visit OUCH UK’s website – a cluster headache charity.