The Gulf War Syndrome is indeed linked to pesticides and nerve agents, US research has confirmed.
A third of veterans of the 1991 war have experienced fatigue, muscle or joint pain, sleeping problems, rashes and breathing troubles.
A US Congress-appointed committee now says the problems were perhaps related to a particular class of chemicals - an anti-nerve gas agent given to troops, pesticides used to control sand-flies, and the nerve-gas sarin that troops may have been exposed to during the demolition of a weapons depot.
The Committee had analysed more than 100 studies in the research.
Dr Beatrice Golomb, the committee's chief scientist, said that genetic variants made some people more susceptible to such chemicals.
When exposed, these people ran a higher risk of illness, she said.
"Convergent evidence now strongly links a class of chemicals - acetyl cholinesterase inhibitors - to illness in Gulf War veterans," Dr Golomb told Reuters.
Dr Golomb said a lot of attention had been given to psychological factors in illness among Gulf War veterans.
But unlike the most recent conflict in Iraq, the ground conflict during the 1991 Gulf War lasted only a few days, she added.
"Psychological stressors are inadequate to account for the excess illness seen," said Dr Golomb, of the University of California, San Diego.
The study has been published in the Proceedings of the National Academy of Sciences.