HAMBURG — The heat in the kitchens is getting hotter. Life for cooks and chefs around the Western world has grown ever more difficult since healthy diets that exclude everything from gluten to dairy became a super trend.

"We are confronted with this on a daily basis," says Tony Hohlfeld, head chef at Hamburg's gourmet restaurant Jante. "Every evening there is at least one guest who will make a special request."

It may not sound so difficult to fulfill such requirements, but it actually is in a gourmet kitchen where the entire operation hinges on how well every segment in the kitchen "machine" works. Normal cooking is barely possible. But no amount of complaining will change the fact that the customer is king.

Nearly every chef, whether in a local pub or in an haute cuisine restaurant, has stories tell about special requests from customers. They can recall diners who gave the staff an entire list of food intolerances that drove the chef to the brink of insanity, of customers who are supposedly dairy intolerant but had a normal cappuccino at the end of a specially created meal, of entire groups where every single customer had different special requests.

The famous Danish restaurant Noma even had a client who called to book a table for himself and his wife saying that his wife couldn't eat anything that "is small and round."

This is particularly difficult for ambitious and conscientious chefs who want to provide a wonderful and allergen-free menu for those customers who have genuine allergic reactions to certain foods.

It has been scientifically proven that allergies and food intolerances are on the rise. Approximately 30% of all adults suffer from a diagnosed allergy and nearly 5% have a food intolerance, according to the European Centre for Allergy Research Foundation (ECARF). They can develop skin irritations, stomach illness or even have an asthma attack if they eat nuts or drink milk.

But the number of people who forgo certain foods because they think they "cannot tolerate" them is significantly higher than that. They avoid lactose products, foods that contain histamines, such as red wine and cheese, renounce fruit sugars or gluten, avoid peanuts or crustaceans. This indicates that a placebo effect may have come into play. Renouncing certain foods may not really be medically necessary, but for some it eases domestic stress or squabbles.

Rainer Roehl of A'verdis, a consulting agency to organic food companies, believes that lifestyle aspects should not be underestimated. "To choose and consume from the full range of foods available seems to be "out,"" he says. "Being an individual ("you are what you eat!") is nowadays expressed in what youdon't eat."

Impoverished high cuisine

Since December 2014, all restaurants in the European Union are required to either display possible allergens on their menu or otherwise inform their customers of them. European legislation lists 14 "main allergens," such as gluten containing cereals, crustaceans, fish, eggs, nuts and celery as well as mollusks and "products obtained from mollusks."

"Your cooking would be significantly impoverished if you had to avoid all of these ingredients," Roehl says. And the continued trend to vegetarianism and veganism hasn't even been taken into consideration.

Diethard Urbansky, of Munich's Dallmayr restaurant, is one of Germany's top chefs. He leaves nothing to chance given that it's a gourmet restaurant. Customers who have made reservations receive a call the day before their booking to whether they have special requirements.

"There is nothing worse than customers coming in on the day and telling you then that they want a vegan, vegetarian or lactose-free menu," Urbansky says. "That's when things get really hectic." He wants to provide the same perfect dining experience for people with allergies, supposed or real, as he does with his those partaking of his usual Michelin Star menu. But cooking without any of the fatty animal-based foods that give that certain je ne sais quoi to a meal, such as butter, is difficult, he says.

In talking to top chefs and nutritionists alike, you do start to wonder if "free from" cuisine is just a spiced up way to use supposed allergies and dietary quirks and fads to demand a different kind of fat-free cooking. Maybe it's better just to order a green salad instead?