Chefs don't want to poison their patrons, you'd presume. But if you have a food allergy or intolerance, you may be familiar with the game of Spot The Killer Ingredient I play when eating out with my fiancé, who is allergic to bell peppers (which show up in the most ridiculous places, such as on top of a steak sandwich) or my mother, who has a severe potato allergy – the tiniest amount will send her into anaphylactic shock. I've seen waiters nod sagely when she explains this, then bring her a salad topped with crisps.

There are varying degrees of sensitivity – Allergy UK says 2% of UK adults are diagnosed with a food allergy and an estimated 45% of the population suffers from food intolerance. At their most severe, food allergies can kill. We're paranoid enough to put "warning: may contain nuts" on nut packets – or rather, the EU Labelling Directive is clear on the need to provide comprehensive ingredients lists and indicate the presence of the 14 most common food allergens on pre-packed food. New legislation for unpackaged foods won't come into effect until 2014 and while it's a start, it's hardly a complete solution.

When it comes to allergies, restaurant staff can be well-meaning but ill-informed. In separate studies by Brighton and Sussex Medical School and the Jaffe Food Allergy Institute at Mount Sinai School of Medicine in New York, restaurant workers were interviewed about their awareness of allergies. Over a fifth of the respondents in both surveys thought someone with an allergy could eat a small amount of that foodstuff (they can't), and over a fifth thought it was fine to just pick it off a finished meal (it's not).

Despite these and a frankly terrifying list of other misconceptions (38% of the Brits interviewed wrongly believed a glass of water could help to alleviate an allergic reaction, for example), the majority of respondents in both surveys thought they could confidently provide a safe meal for a person with a food allergy.

Then there are the people who hear "allergic" and think "fussy". Of course, some people really are just being fussy, but the problem comes when restaurant staff take it upon themselves to decide who has a genuine allergy and who is just crying wolf.

"So many people claim to have an allergy or intolerance when they don't, so restaurant and service staff don't take it seriously," says food and travel writer Nikki Bayley, who is allergic to mushrooms and jalapeño peppers. "I've swollen up in restaurants after asking if they're in the recipe – including in restaurants that know she's there to review them. "One chef decided there was some sauce I had to try. I spent an hour and a half being violently sick in their bathroom."

"Sometimes they seem to think it's not a big deal and I'm just being fussy," agrees writer Camilla Chafer, who has a milk allergy. "Yes, the sauce has milk in it, now you mention it. Can't you just scrape it off? No, I can't. It's not a choice and I'm not deliberately being awkward. I just don't want to vomit or pass out in your restaurant."

This is something restaurants need to recognise, says Alex Gazzola, author of the Food Allergy and Intolerance Ink blog. "There's a psychological side to food sensitivity – people may feel frightened, ashamed, anxious or embarrassed." It's hardly pleasant being the person who kicks up a fuss or sends their meal back.

It would be far too cynical to assume restaurants simply don't care and don't want the hassle of catering for customers with allergies. After all, those that do it well can count on enduring customer loyalty and positive recommendations - and nobody wants to do it badly, do they? When I phone some restaurants to ask if they can cater for people with allergies, they all insist they can but, from experience, I already know otherwise.

It's not as if staff would have to learn a million allergies and ingredients, they just need to listen when someone expresses concern about the menu. Gazzola also recommends that dishes are given clear, descriptive names (as opposed to "Chef's Special") and that menus be posted online so they can be studied in advance. He also advises diners with allergies to phone ahead if possible to ensure their needs can be accommodated.

Restaurants are not the sole culprits here: the worried well aren't helping either. "I'm not saying restaurants are terrible and they need to sort their act out," says Bayley. "People need to stop complaining about things that aren't the matter with them."