The number of people with food allergies worldwide is increasing, and the greatest increase has been seen in children. Researchers estimate that around 17 million Europeans, or 2% of the population, suffer from food allergies, and that food allergies in children increased by around 50% between 1997 and 2011.

Theoretically, any food can cause an allergy, although the most common - accounting for 90% of all reactions - are eggs, milk, peanuts, nuts, fish, shellfish, cereals containing gluten, soy, celery, mustard, sesame seeds, fish, shellfish and sulfur dioxide: The infamous 14 major allergens. Consumed allergens can cause skin rashes, itching and swelling of the mouth and tongue, and in extreme cases even anaphylaxis.

There is currently no cure for food allergy, and disease management relies on avoidance of offending foods and an emergency treatment plan in case of exposure. Life-threatening reactions can be caused by even traces of trigger foods, meaning patients and families live with fear and anxiety. The ensuing dietary restrictions can become a burden on social and family life.

Why the sudden rise in food allergies?
The real cause of allergies is not 100% known. Of course, genetics has a lot to do with it. If your parents have allergies of any kind, chances are you have them too. If you or a close family member has asthma, it also increases your risk of developing allergies. Two 2016 studies in Science Translational Medicine suggested that signs of food allergies may already be present at birth in immune cells and/or in monocytes, a type of white blood cell. And it is well known that children with eczema, who often have an inherited allergic tendency, are at higher risk of developing food allergies.
And yet, genetics is not entirely to blame: The frequency of food allergies has increased over the past 30 years, especially in industrialized societies. The exact extent of the increase depends on the food and where the patient lives. We now know that allergy rates are lower in developing countries. They are also more likely to occur in urban than rural areas. A 2013 study in JAMA Pediatrics found that foreign-born children who live in the United States have a lower risk of developing allergies and, more interestingly, that risk increases the longer they stay here. Allergies and increased food sensitivity are then thought to be likely environmental and related to Western lifestyles. Factors can include pollution, dietary changes, and less exposure to microbes, which alter how our immune system responds.

Improving hygiene is among the other likely causes, as children do not get as many infections. Parasitic infections, in particular, are normally combated by the same mechanisms involved in the fight against allergies. With fewer parasites to fight, the immune system turns against things that should be harmless.
Another idea is that vitamin D can help our immune system mount a healthy response, making us less susceptible to allergies. Most people around the world don't get enough vitamin D for a number of reasons, including spending less time in the sun. In the United States, the rate of vitamin D deficiency is thought to have nearly doubled in just over a decade.

But the overriding factor may be the growing reliance on processed foods, depleted of natural compounds, and the growing consumption of artificial chemicals (food preservatives, dishwasher detergents, etc.) that we have not evolved to handle with our natural defense. 

Even if we don't have food allergies today, we might have them in the future. And while we can't totally control our environment, we can control our lifestyle and our diet.

Further reading
Halken et al., EAACI guideline: Preventing the development of food allergy in infants and young children (2020 update), Pediatric Allergy and Immunology, 2021, https://doi.org/10.1111/pai.13496
Florsheim et al., Food allergy as a biological food quality control system, Cell, 2021, https://doi.org/10.1016/j.cell.2020.12.007
Sanos A., Why the world is becoming more allergic to food, https://www.bbc.com/news/health-46302780
Levine J. What are food allergies, and why are they becoming more common?,  https://crosstalk.cell.com/blog/what-are-food-allergies-and-why-are-they-becoming-more-common