A team led by Dr Tom Kurt, in Texas, found that doses of three chemicals used to protect Gulf war soldiers from nerve gas attack and insects were harmless alone, but mixed together could cause neurological problems in animals.
Veterans last night welcomed the results as the first scientific evidence supporting their claims that a variety of symptoms dubbed Gulf war syndrome were caused this way.
They claim 19 British Gulf war soldiers have died since returning from the conflict. Around 1,000 more hope to claim damages from the Ministry of Defence for chronic fatigue, headaches, memory loss and aching limbs they believe to have been caused by the drugs.
But while the MoD said the US findings would be examined, a spokesman said there was nothing to replace the inoculations at present. They were necessary and would be continued. "When you are sending people into a situation where chemical attacks are a threat, you either have to say take the pills or take the risk," he said.
Neither the British nor American government has accepted the existence of a specific condition called Gulf war syndrome.
Dr Mohamed Abou-Donia, one of the researchers, said the Army had eliminated any other possibility and veterans should be now examined for signs of chemical poisoning. "We're not saying this is Gulf war syndrome, but we're saying this deserves a look," he said.
The team gave healthy chickens, whose neurological pathways are similar to those in humans, separate doses of the nerve gas pill pyridostigmine and the insecticides DEET and permethrin. Taken alone, even doses three times greater than soldiers receive did not harm the chickens.
But any two chemicals together gave them diarrhoea, shortness of breath, stumbling and other symptoms. The three taken together paralysed or killed some of the birds.
Glasgow specialist Dr Goran Jamal, who recently discovered proof of nerve damage in Gulf veterans, said it would be "foolish" to ignore this research.
"What it shows is that it is now not enough to be saying that such and such is safe because it has been used before. We have to look more at not what the substances do in themselves but what they do in combination with others."
Hilary Meredith, a solicitor representing some of the British veterans, said the results were "extremely good news" in their fight against the MoD.
"If this proves the causal link between the inoculations and the symptoms it is a major step forward," she said.
Veterans said there was now no excuse for the ministry to continue "delaying tactics".
Major Ian Hill, chairman of the National Gulf Veterans and Families' Association, said: "We call on the Government to speed up their evaluation and research ... which will hopefully lead to a definite answer to the problems of the suffering Gulf war veterans."
Tony Flint, a medic in the Gulf, added: "It seems strange that the research done by the British and American governments can't find anything but individual independent researchers have found this."
Dr David Clark, Labour's defence spokesman, said that the Government should now recognise the existence of Gulf war syndrome.Reuse content