People who suffer from cluster headaches say there's no worse pain in the world and very little can relieve it. Now, a new study finds that something can: pure oxygen.

High-flow oxygen helps to relieve the pain quickly, confirms a new study in JAMA, the Journal of the American Medical Association.

Cluster headaches, which affect about 0.3 per cent of the population, are often nicknamed "suicide headaches" because of the excruciating pain they cause.

The attacks can last from minutes to hours and can occur several times a day. Attacks usually occur in "clusters," lasting for weeks or months, separated by remissions of months.

Why some people suffer from the headaches is unknown, but it's thought to relate to genetic malfunction of pain control centres in the hypothalamus and brain stem.

Over-the-counter medications are usually ineffective against the headaches, since they take too long to begin working. Most patients treat their pain with injections of sumatriptan (sold as Imitrex). But patients are warned not to use the drug frequently, since it carries serious side effects, including the risk of heart attack. For that reason, the drug is not suitable for patients with any form of heart disease.

While many cluster headache patients have turned to high-flow oxygen to relieve their symptoms, there hasn't been a lot of good study on its use that compared the therapy back to back with a placebo.

Now, the largest study to date on the high-flow oxygen treatment finds it is effective for cluster headaches.

Researchers, led by Anna S. Cohen, of the National Hospital for Neurology and Neurosurgery in London, found the majority of patients who received oxygen treatment reported being pain-free or having adequate pain relief within 15 minutes of treatment.

The study involved 76 adults with cluster headaches. The participants treated four cluster headache episodes alternately with either high-flow oxygen through a face mask for 15 minutes at the start of an attack or regular air through a face mask. Patients did not know which treatment they were receiving.

Among those breathing in oxygen, 78 per cent were pain-free or had adequate pain relief within 15 minutes of treatment. That's compared with just 20 per cent of those who were treated with just air.

Oxygen treatment was also superior to the placebo air treatment for pain relief at 30 and 60 minutes after the start of the cluster headache attack.

There were no side effects noted with the drug-free oxygen treatment.

The researchers say their study confirms what many headache patients and their doctors already knew about oxygen.

"This work paves the way for further studies to optimize the administration of oxygen and its more widespread use as an acute attack treatment in cluster headache, offering an evidence-based alternative to those who cannot take triptan agents," write Cohen and her colleagues.

The study was funded in part by Linde Industrial Gases, a German supplier of industrial and medical gases.