Barry Green, 63, a resident of Plymouth in Devon, claims that he had to spend a week in hospital with blisters, breathing problems, pneumonia, and eventually heart failure.
The father-of-four bought the brown leather couch worth 545 pounds from Land of Leather a year ago, but soon began to suffer health problems.
He is now seeking damages from the firm and its manufacturers, Chinese firm Eurosofa, via a High Court legal action.
Green claims that his heart failure has been brought on by sachets of an anti-mould fungicide under the cushions, which contain the chemical dimethyl fumarate.
"At first I couldn't catch my breath. One night the doctor came out and he had me on oxygen because I couldn't breathe," the Telegraph quoted him as saying.
"I'm so angry. This should never have happened.
"I was quite a fit guy before and now I'm on so many tablets you wouldn't believe it. I have to walk up the slope to my house; it's only 20 or 30 feet and it's gradual, but I get really out of breath. I used to do gardening and all sorts before, but now I wouldn't even bother trying.
"The last year has been a tough one - it appears all because of this sofa. I don't know who to blame, but I'm appalled," he added.
A spokesman for Land of Leather said: "As the subject matter of the report is part of ongoing High Court proceedings, the matter is subjudice and as a result we are advised by leading counsel that it is improper for us to comment."
Eurosofa not the first Chinese firm to be linked to rashes, for at least 1,000 people claimed that they were burnt by leather sofas from the firm Linkwise earlier this year.
They had been treated with a fungicide to stop them going mouldy in storage, but the substance triggered some violent cases of eczema in some customers.