Millions of people have imaginary allergies and food intolerances, according to a survey last week. Many of them have diagnosed themselves online; one in 50 says they only noticed their “problem” when a friend had similar symptoms; and 39% of people questioned think it is “trendy” to claim a food allergy. Twelve million people claim to suffer from allergy or intolerance, of which less than a quarter are medically diagnosed.

Is this not completely hilarious? There are more than 3m people walking around droning on about “lactose intolerance” this and “issues with wheat” that, and they’re complete fantasists as well as the most tiresome and bad-mannered dinner party guests.

I understand that allergies (where the reaction is dramatic and occasionally life-threatening) and intolerances (where the reaction is unpleasant but less extreme) do actually exist; I have a small nephew whose medically diagnosed intolerances are so severe that he is under the care of St Thomas’ hospital in London. His parents carry an EpiPen. So I’m not one of those people who think the very idea of allergies is nonsense.

But I do loathe the way in which people – usually women on a diet – turn something commonplace and understandable, such as not eating bread because it makes them fat, into a look-at-me-I’m-special, cod medical issue. If such people simply said, “I try not to eat bread because it turns me into the Michelin man”, everyone would be perfectly understanding. But that would be admitting to vanity, which won’t do: far better to pretend we actually have a condition.

I am carbohydrate-phobic myself: if I eat stodge I get fat. But the words “wheat allergy” have never passed my lips, because I don’t suddenly break out in welts and have difficulty breathing if I so much as glimpse a piece of Poilâne. If I go out to supper and my host serves bread-and-butter pudding, I eat a little of it because I am polite. I can’t think of anything ruder than being asked to dinner and faxing the host a great list of the things I will and won’t eat or of emitting great public wails of distress at the sight of potatoes.

Few people have such scruples: many consider it perfectly normal either to e-mail you their dietary requirements or to turn their nose up at food you have spent hours cooking. It drives me mad – particularly when people with real and serious conditions such as diabetes or Crohn’s disease never make a fuss and just quietly leave what they can’t eat without you even noticing.

Our attitude to food in this country is deranged. While millions of people invent allergies in the tragic hope of seeming as special as some little half-starved, half-mad Hollywood starlet (or of legitimising their borderline eating disorder), millions more of them pretend that food that provenly harms them – and more to the point their children – is absolutely fine to eat. (By the way, our children are now so routinely obese that doctors have had to change the name of “adult onset” diabetes to type 2 diabetes because so many – very – young people are showing signs of the disease.)

While the Food Standards Agency (FSA) recently acknowledged that some E numbers do actively harm, it seems strangely reluctant to actually do anything about it. Many people have known of the link between certain additives and disturbed behaviour for, ooh, a good 20 years, since Maurice Hanssen’s E for Additives was first published.

Hyperactivity is a common result of consuming, among others, E122, or carmoisine, which is present in flavoured yogurts and soft drinks. It can also be triggered by E104, quinoline yellow, which is banned in the United States, Japan and Norway for its link with hyperactivity in children. But who needs food bans when you have Ritalin?

What is especially appalling about this is that the children who eat rubbish food and have behavioural difficulties are not necessarily the kind whose parents angst over additives or the strange fluorescence of certain fizzy drinks or pore over reports in medical journals. The only way of helping these people and their children is an outright ban.

However, the FSA ignores all the evidence (and there’s plenty more where it came from) and continues to claim, wildly, that it is acting reasonably in not outlawing these additives – this despite a written plea last week from children’s campaigners, teachers, health groups and environmentalists, who joined forces and wrote to the FSA asking it for a ban. Back in May a molecular biology expert at Sheffield University claimed that chemicals in soft drinks could actually alter the structure of children’s DNA and cause serious damage to cells.

The additive in question, E221, is in Pepsi Max and Fanta, among others; lab tests at Sheffield suggested that it may even be linked to degenerative diseases such as Parkinson’s in later life. The FSA and the drinks manufacturers in question said they felt that the chemical had been properly assessed and that there wasn’t a problem. The food additives industry is worth £12.4 billion.

In other food news, it was also reported last week that the preponderance of peanut allergies may actually be caused by the government’s advice to avoid peanuts during pregnancy (a new one to me, I must say). An all-party House of Lords science and technology committee will next week recommend that this advice, which dates from 1998, is withdrawn immediately. “Evidence suggests that countries which expose young children to peanuts have much lower or nonexistent cases of peanut allergy,” a source told a London newspaper.

Honestly: no wonder every other person seems to have a bizarre, phobic, unnatural relationship with food. As I never tire of pointing out to pregnant friends who are longing for the odd glass of wine, our mothers’ generation smoked and drank their way through pregnancy with no extra folic acid and no adverse effects whatsoever – and ate peanuts, blue cheese and the rest.

But we have in the past 15 years or so chosen to decide, strangely, that not only is pregnancy a sort of illness, but that being alive itself is a sort of illness that must be self-diagnosed, self-medicated and self-cured.

It is unbelievably tiresome and very damaging: what used to be called “faddy eating”, which made everyone roll their eyes in exasperation, is well on the way to becoming the norm – and far from rolling our eyes, lots of people are applauding. We are fortunate to know so much about the food we eat and about the chemicals we should avoid. All that’s left is to tuck in like a normal person and have a little of everything in moderation.

india.knight@sunday-times.co.uk

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