Many vegetarian ready meals contain Quorn

There have been concerns that the meat substitute could cause stomach upsets.

But Swiss and German doctors have detailed the case of an asthmatic who had a severe allergic reaction to the food.

The patient, a 41-year-old man with a long history of asthma, developed a severe skin reaction, including blistering, and suffered an asthma attack an hour after eating Quorn.

Intolerance to Quorn is much less frequent than to other foods such as soya and dairy products Food Standards Agency statement

Scientists carried out skin prick and food reaction tests and laboratory analysis to confirm what had provoked the allergic reaction.

Quorn was the only food to which he proved to be allergic.

The researchers suggest the attack was probably caused by a reaction between the "mycoprotein" in Quorn and a human allergen in the patient.

Protein

A spokeswoman for the Food Standard Agency told BBC News Online it would not be taking any immediate action, but added: "As with any new research that's published, we will be assessing this paper and any implications it may have for our advice on Quorn."

On its website, the FSA currently states: "There have been some reports of intolerance to Quorn, but this is not surprising, because it has a high protein content (allergens are usually proteins).

"Intolerance to Quorn is much less frequent than to other foods such as soya and dairy products."

Statistics show adverse reactions are reported for one in 146,000 people who ate Quorn, compared to one in 35 who ate shellfish and one in 350 who ate soya.

The US Centre for Science in the Public Interest campaigns for Quorn to be withdrawn because of the reported allergic reactions.

It claims to have received over 600 complaints from consumers who said they had suffered reactions including vomiting and diarrhoea after eating the product.

Michael Jacobsen, the CSPI's director, told a national newspaper he was shocked that the FSA had "nonchalantly allowed this product to remain on the market, given the ample evidence of the misery it causes.

"As the medical evidence mounts, one hopes that the FSA just doesn't wait for someone to die from Quorn."