A man says fumes from a farm's slurry pit have "split" his tongue.
Mike Hill, from Templeton, Devon, says a "horrendous" smell started coming from the farm last year, which it is claimed has made residents feel ill and caused them to leave their properties.
Authorities are testing air and water near the farm, which houses about 150 cows.
But farmer Winston Reed says he will take action against what he says are "false comments".
Mr Hill says that along with tongue fissures, he has suffered from irritated eyes, coughing and constant thirst.
"You get a really hot, peppery taste in your mouth and you just can't get rid of it, it's in the back of your throat," he said.
Other neighbours have complained of phlegm, high blood pressure, breathing difficulties and retching.
But Mr Reed, who runs Crossparks farm, says the allegations are simply not true.
"None of our cows or staff working at the unit display any of the symptoms alleged to have been caused to the complainants," Mr Reed said.
Cow blood tests
"I have asked for blood tests to be taken of our cows on site along with veterinary reports, samples to be taken of the slurry, additional odour monitoring to see if indeed this unit is as the allegations portray."
Mr Reed says he has also asked for a breakdown of how much the complaints have "cost the public taxpayer".
Mid Devon District Council's environmental health department confirmed it was investigating the complaints.
"Environmental health are conducting an investigation into complaints of statutory nuisance concerning farm operations at Crossparks and Cleave Farm, Templeton, Tiverton, Devon made by persons living in the surrounding area," a spokesperson said.
"Devon County Council's Public Health team and Public Health England are continuing to liaise with us during the course of our investigation."