Ben Feltwell is allergic to eggs. Which is why, on a trip to Amsterdam six years ago, he made absolutely sure there was no egg in the pastry he ordered at a French restaurant. “I placed the order and told the waiter I was allergic,” the 31-year-old digital marketer recalls. “He went off and checked with the kitchen. He spoke with the chef and came back and said it was OK. When the meal came out I said: ‘Can you guarantee this doesn’t have egg in it?’ The waiter said: ‘Of course!’”

Reassured, Feltwell bit into the pastry – and immediately had an allergic reaction. He can tell within seconds if a food item contains egg, because his lips begin to tingle.

When the chef came out of the kitchen, he was on bellicose form. “He said: ‘Well, we make the pastry with egg, but then we fry it and bake it, so there’s no egg left!’” Feltwell took a taxi back to his hotel, where he spent the next four hours vomiting. To add insult to injury, after he left, the restaurant attempted to charge his companions for his meal.

Feltwell laughs in disbelief as he remembers the incident. But it’s not the first time his egg allergy hasn’t been taken seriously, and it probably won’t be the last. “It’s treated as a dislike, rather than an allergy,” he explains. “I’ve had a few chefs and waiters tell me to my face that it’s not a real allergy, but a preference. I say: ‘I think my doctor would beg to differ.’” And it’s not just chefs that Feltwell needs to watch out for. Once, on a camping holiday, a companion slipped an egg into his curry. “He was trying to make the point that my egg allergy wasn’t real.” He sighs. “It ruined the holiday.”

For those with food allergies and intolerances, Feltwell’s experiences may seem familiar. In August, a woman wrote to the Cut website’s advice columnist, Heather Havrilesky, asking how to deal with in-laws who put mushrooms in her food, even though she was severely allergic to them. Her in-laws weren’t just callously disregarding her allergy – they seemed actively set on harming her, even slipping mushroom powder into the mashed potatoes during a family meal. “What’s worse is my husband told me that mushrooms were not a common dish served by his parents before he started dating me.”

Ignoring allergies can kill. In July 2016, 15-year-old Natasha Ednan-Laperouse died on a British Airways flight after suffering an allergic reaction to a Pret a Manger baguette she had bought at Heathrow airport. She hadn’t realised the baguette contained sesame, to which she was severely allergic, because outlets that make food on-site aren’t required to put allergen advice on their wrappers. There have been other deaths in recent years, including that of 15-year-old Megan Lee, who died after eating a takeaway meal containing peanuts in 2016 (the takeaway’s owner and manager were convicted of manslaughter). And an inquest is considering whether 18-year-old Owen Carey, who died in his girlfriend’s arms following an allergic reaction in April 2017, was served a meal contaminated with wheat and dairy – to which he had allergies – at a London burger bar.

“People are realising that those with food allergies can die on your premises,” says Leigh George of the charity Allergy UK. She welcomes the introduction of Natasha’s law, to be implemented in 2021, which will require food businesses to publish allergen advice on all pre-packaged food. But George urges the government to go a step further and require catering outlets to list every ingredient on their menus, not just the main allergens, so consumers can make informed choices.

As a nation, we’re becoming more allergic to the food we eat. According to the Food Standards Agency, in the UK an estimated 2 million people have a food allergy, with an average of 10 food-allergy-related deaths a year. The NHS says that allergy-related hospital admissions increased by 33% between 2011-12 and 2015-16. Meanwhile, Allergy UK reports that between 6% and 8% of children have some form of food allergy. “The diversity of our diet is one of the drivers of this rise in allergies,” says Dr Isabel Skypala, a consultant allergy dietitian “as people are becoming allergic to food they haven’t eaten before – like jackfruit.”

Even if you don’t have a life-threatening allergy, having someone disregard your dietary needs can have serious health consequences. Sebastian Clark, 25, a graphic designer from London, was diagnosed with the autoimmune disorder coeliac disease when he was 19. Eating even a trace of gluten will make him extremely ill. “Every time I eat gluten, I lose half a stone in weight.” Despite this, family and friends don’t always prepare his food with due care – Clark tells me about one meal at a relative’s house where she slow-cooked a joint of beef. “I said: ‘This tastes really nice, it’s so rich in flavour.’ And she said: ‘I put some craft ale in it.’” (Most beer contains gluten.) It took him three weeks to recover from that meal.

Clark isn’t the only person to struggle with family members. For Cathy Jones, a clerical officer, meals at her boyfriend’s mother’s house are always fraught with risk because she refuses to accept that Jones’s irritable bowel syndrome – which is triggered by onions, spring onions and shallots – isn’t make-believe, and keeps slipping alliums into her food. This year, the mother served Jones a sweet chilli dish – and made a point of telling her that the recipe had called for spring onions, but that she had left them out. But when they sat down to eat, the dish seemed to have chunks of onion in it. After peering suspiciously at her food, Jones asked the hostess outright – and was assured that it was only a piece of ginger. But it still looked remarkably onion-like, so her boyfriend tried a bite.

“He said, ‘Mum, this tastes like a shallot,’” Jones laughs. “She said: ‘OK – you’ve caught me!’”

Jones is remarkably good-humoured about it – she jokes that she will marry her boyfriend only when his mother accepts she can’t eat onions. But the bit that really winds her up is that the mother doesn’t eat onions herself. “They give her heartburn! She avoids them as well.”

The drive home from the mother’s house takes nearly two hours. If Jones unwittingly eats onion before she gets into the car, it’s not pretty. “We’ll need to make an emergency stop somewhere. Luckily, that hasn’t happened in years.”

What makes someone repeatedly ignore someone’s dietary needs, to the extent of compromising their health? Jones doesn’t believe it’s malicious: “I think she thinks I don’t like the taste, so if she makes it taste better, I’ll like it.” But it’s also possible that the increasing popularity of influencer-driven elimination diets has made it harder for people with legitimate medical needs to be taken seriously.

This, after all, is an age where Gwyneth Paltrow’s Goop advocates an annual “detox” that cuts out caffeine, alcohol, dairy, gluten, corn, nightshades, soy, refined sugar, shellfish, white rice and eggs; when supermodel Elle Macpherson endorses the alkaline diet; and when “clean-eating” gurus such as Madeleine Shaw and Amelia Freer secure lucrative publishing deals. Free-from regimes are sold as the cure to all of life’s ills, boosted by a swarm of quasi-reputable nutritionists, often on beautifully photographed blogs.

Tanya Khan, 21, a student from Warwick who is lactose-, egg- and gluten-intolerant, gets frustrated when her dietary requirements are viewed as a lifestyle choice. “You can’t put someone’s health condition on a par with veganism,” she says. “It’s not fair. If they ate meat, something physically wouldn’t happen to them – but if I had ice-cream, I would be really ill.”

Meanwhile, food outlets that treat terms such as “gluten-free” as little more than buzzwords gamble with people’s health. Chloe Marvin, 23, a civil servant from London, is intolerant to gluten, and allergic to nuts, beans and sesame. She recently got into a row with a food-truck worker, after she saw him put breaded ham into her “gluten-free” crepe. “I said: ‘You’ve advertised it as a gluten-free crepe; I can’t eat gluten.’ He said: ‘Well, the crepe is gluten-free; this is how ham comes.’”

Nathalie Newman has seen the damaging effects of influencer-driven fad diets first-hand. The 38-year-old, from Buckinghamshire, runs the popular blog the Intolerant Gourmand, which she founded after her son Callum was diagnosed with 28 allergies, eight of which are life-threatening. Newman works with chefs to make their menus allergy-safe. “They tell me that patrons come in and say they’re dairy-free or gluten-free, or even coeliacs, so they take it seriously, and then a dessert will go past and they’ll say: ‘Oh, that looks amazing.’ The chef says: ‘You can’t eat that,’ and they’ll go: ‘Oh, it’s OK – a little bit won’t hurt.’ So when someone who has a true allergy comes in and says: ‘I can’t eat that,’ who do they trust and believe?” Newman is convinced this behaviour puts people at risk. “It’s quite scary.”

When restaurant staff conflate genuine allergy sufferers with fussy eaters, patrons with legitimate health conditions find themselves under scrutiny. Jenny Allen, 35, a teacher from Oldham, follows a gluten-free diet to mitigate the symptoms of her postpartum thyroiditis. (Some believe that autoimmune conditions such as thyroiditis can be managed with the help of a gluten-free diet, although the scientific evidence is not conclusive. Allen herself believes that avoiding gluten has helped.) Recently, she was in a cafe and asked for a gluten-free meal. “They said: ‘Oh, it’s all the rage at the minute, isn’t it? It’s a trendy thing to do.” The comment made her feel “silly and ridiculous”. In particular, Allen chafed at having to justify herself to a perfect stranger. “Having to explain something really complex over a baguette,” Allen sighs. “I’m like: I flipping loved bread before! I’d rather be sitting here eating a crunchy baguette, and not having to explain my backstory.”

If restaurant staff aren’t properly trained, supposedly allergen-free meals can easily be contaminated. Feltwell was made sick at an Italian restaurant that prepared his food on the same work surface as a florentine pizza, which has egg on it. Marvin had to run out of a south London restaurant recently after going into a sesame-induced anaphylactic shock from a shakshuka dish. She chose not to complain, even though she had disclosed her sesame allergy when ordering. “My friend said: ‘Do you want to say anything? I said: ‘No, not really.’ It makes me really uncomfortable. Having an argument in a restaurant is unpleasant and draining.”

It’s not only restaurant staff you need to worry about – Khan has grown used to being accidentally poisoned at home. “I get lactose-free butter and other people use it and you end up with breadcrumbs in there,” she sighs.

When you have specific dietary needs, eating out can feel like an ordeal. “It creates so much anxiety ... there’s always a huge buildup to food,” says Marvin. She tends to patronise places she has eaten at before, and knows to be safe. “Everyone else can say: ‘This looks like a nice place,’ and wander in there. But that gives me the fear. For me, eating out is a huge thing. The evening before, I need to research the restaurant, and check their allergy menu. And even when I’m out, I feel anxious beforehand and anxious when I’m eating. Your trust has been broken by all these bad experiences.”

Some people don’t think the risk is worth it – such as Mike Dancer, 53, a retired teacher from Reigate, Surrey, who follows a ketogenic diet to manage his epilepsy. (These low-carbohydrate, high-fat, controlled-protein regimes are proven to help control seizures in some people.) “I tend to travel with Tupperware boxes full of food,” Dancer says. Once, at an international conference in Italy, he was unable to eat any of the food provided – so he simply didn’t eat for five days.

Having specific dietary needs is often socially isolating. “It can rule your life,” says George. “Where the majority of us take it for granted that it’s our birthday, or a Friday night, and we can go out for dinner, imagine how you’d feel if you thought that eating that meal could kill you. It makes socialising extremely difficult and stressful.”

On work trips, Marvin tends to eat separately from her colleagues, in restaurants she knows to be safe.

Life is so much easier when everyone respects your needs. After years of carrying his lunch around with him, Dancer was recently able to enjoy a meal of barbecued fish, avocado and salad with friends at Rockfish in Brixham, Devon. “It was a very inclusive feeling, to be honest. To be part of the group that’s eating is very important. I felt at long last that I was allowed back with the group.”

Some names have been changed.

• This article was amended on 11 September 2019 because an earlier version referred to Stansted airport, when Heathrow was meant. This has been corrected.