Akhmed Zakaev, a representative of the Chechen rebel leadership who lives in London, asked for an "urgent international investigation" in a letter to Rogelio Pfirter, director-general of the Organization for the Prohibition of Chemical Weapons.
About 80 people, including 58 children, have fallen ill recently in several towns with breathing problems, headaches, and cramps.
Zakaev suggested that chemical poisoning was to blame rather than psychological factors as claimed by doctors.
Some local officials said the symptoms could indicate a form of nerve-gas poisoning. But Russian medical experts sent to Chechnya have firmly rejected those allegations, saying the disease had psychological causes.