Gulf War Illness (GWI), also known as Gulf War Syndrome, is a multi-symptomatic disorder that has affected veterans since their deployment in the war between 1990 and 1991.
The medical world has puzzled and probed why Gulf War veterans have suffered the debilitating syndrome that includes symptoms of fatigue, muscle pain, cognitive problems, insomnia, rashes and diarrhoea.
Now researchers from Griffith University have found out why.
They say the illness is likely caused by intense exposure to hazardous biological and chemical agents and the effect they have on cell structures.
Cell structures within the human body are sensitive and vulnerable to these agents, causing faulty cell function.
Gulf War Syndrome has affected veterans since their deployment in the war between 1990 and 1991. (Dan Himbrechts/AAP PHOTOS)
Author of the study Sonya Marshall-Gradisnik says the research has found integral cell structures that transport calcium are defective in veterans.
Calcium within cells is a signalling molecule that regulates essential functions such as muscle contraction, nerve function and hormone secretion.
"Our study reveals a crucial dysfunction in cell ion channels, specifically the transient receptor potential ion channels, in veterans with GWI," Professor Marshall-Gradisnik said.
"This discovery is a significant step forward in understanding this baffling and complex illness."
For Gulf War veteran and illness advocate Ian Allwood, being believed is a huge step.
"This research is life-changing for the Gulf War vets," he said.
"For those in the veteran community that have been suffering, this is the first step in identifying a causal factor.
"This is groundbreaking research that will hopefully open pathways to treatment for the often-debilitating symptoms."
Fellow author Etianne Sasso says the findings are crucial in demystifying the illness and offers scientific evidence validating the condition for long-term sufferers.
"This breakthrough in understanding the cause of GWI now provides hope for researchers to be able to develop new treatments to improve the future for our veterans," Ms Sasso said.
The illness affects between 25 and 32 per cent of the nearly one million veterans from 41 countries who served in the war.
More than 1800 Australians served, mainly in the navy.
Many of the defence service men and women were exposed to anti-nerve agent drugs, insecticides, nerve agents and depleted uranium.