In England, I once found myself sat at a table with colleagues on a training course and amongst them was a coeliac, someone allergic to nuts, someone allergic to lactose, and someone allergic to egg products. Now I am sure that each of them were convinced of the reality of their allergy but given the actual incidence of these allergies in the population, the probability of getting all four of them sat around the table in the random selection of people that I knew, was incredibly low. It turned out that only one of them had ever been tested for allergy, the coeliac, who had undergone extensive hospital tests to diagnose serious gut problems from which they had been suffering for years.
The others genuinely believed themselves to be suffering from their allergies and meticulously avoided the suspect food, changing their diet extensively. They had self-diagnosed. Nevertheless, they uniformly said that they were still suffering from the symptoms. The peanut allergy sufferer said he didn't even carry an Epipen.
The incidence of coeliac disease is around 1 in 250 though the number actually diagnosed and treated is around 1 in 4700. So there are lots of sufferers out there undiagnosed and untreated. Coeliac disease is serious and leads to long-term gut damage if not treated and controlled.
Lactose intolerance is not an allergy but a problem in breaking down the sugar lactose. It is thought to affect 1 in 9 for Caucasians but rises up to around 9 in 10 for Asian Americans. It's caused by an enzyme defect and it can be tested using three easy hospital tests: feeding the patient lactose then measuring the blood sugar level as it is metabolised over a few hours; measuring the hydrogen concentration in the patient's breath; and measuring the acidity of the stools. Lactose intolerance is inconvenient but not serious and is easily managed. Most sufferers never consume enough lactose at a time to generate symptoms. Those who have the enzyme defect and experience symptoms, simply avoid milk products.
Peanut allergy affects 1 in 200 and is extremely dangerous, being able to bring on anaphylactic shock. To deal with this danger, sufferers carry an epinephrine pen to administer an injection at the onset of an attack. During the attack, the airways swell and constrict leading to choking and epinephrine is the only treatment that works quickly enough.
Intolerance to egg proteins is mostly seen in young children and affects around 1 in 50 of the population, but most sufferers have outgrown it by the age of ten or twelve. It is not considered serious but can be very inconvenient.
So in my group of eight people, I had the 1 in 250 coeliac, the 1 in 9 lactose intolerant, the 1 in 200 peanut allergic, and the 1 in 50 egg avoider. The chance of that happening is around 1 in 5500, so it was much more likely that at least one of them had incorrectly self-diagnosed.
Although there is some evidence that allergies are on the increase, the figures are ambiguous. Certainly there are very many more people being tested than previously so the recorded figures would be expected to rise even if the incidence had not. But also the increase in testing gives rise to a high number of false positives.
False positives are where the allergy tests indicates that the patient has the allergy when they don't. This can seriously skew the results, especially when the accuracy of the test is around 90% and the incidence of the actual allergy is low. Suppose an allergy has an incidence of 1 in 500 of the population, and the test is 90% accurate. Because the incidence is low, the number of false positives far outweighs the correct ones. In fact, in this case, you'd be only 2% likely to have the allergy if you received a positive result - work out the figures for say a sample of 10,000 tests. So even if the test seems to have a high accuracy, for rare or uncommon conditions, the tests have to be exceptionally accurate to have any validity at all. Around 50% of skin and blood tests for allergies are false positives.
That might be one reason why so many people are diagnosed with allergies, though of course, they might actually have them. The problem is that establishing the facts is an expensive and time-consuming process and most patients just go away and avoid some element of their food. That explains why many of them continue to suffer the same symptoms. Self-diagnosis will be even less accurate.
There may well be an increase in the incidence of allergies, but nothing like as fast as the increase in self-diagnosed people who claim to have them. The majority of those who say they have allergies, don't. They genuinely believe they do, but they don't.
Undoubtedly another reason could be the Gucci effect. It is now seen as particularly chic to have an allergy. Avoiding certain foods makes a talking point of someone's dietary behaviour, singling them out as special. Their self-diagnosis may simply be influenced by someone else saying that they had a dietary problem, that they were special. This sort of herd behaviour is not uncommon and works in fashion and sales generally, and marketing strategies rely on it. The worried well is a big market.
Gut problems are notoriously difficult to diagnose and the tests can often be expensive and time-consuming. With so many patients eager to be diagnosed allergic to something, it's no surprise that there is an increase in those who give themselves that label. Once they are tuned in to thinking there is something wrong with their gut, they will be more susceptible to ideas about detox, food supplements, special diets and the like.
The sensible advice has to be to get a medical practitioner to investigate the symptoms and if necessary to undergo medical tests. Even those tests may not give the right results so it's important not to jump to conclusions. An upset stomach doesn't mean an allergy, even if it follows eating some specific foodstuff. Identifying a potential allergen can take a long time and involve methodical controlled trials.
Bob Lloyd has studied in four universities and has degrees in Biochemistry, Mathematics, and Computer Science. After a long career in publishing, teaching, and software engineering, he is now retired and lives in Andalucia in the South of Spain with his wife and rather ancient cat.
