This is an absolutely ridiculous claim, it's very clear that you have never met anyone with an allergy (or cared to ask someone about their experience if you have)
Actually I have them in my family (epi pen and all), but I've met many more people with false allergies that use them to justify disordered eating habits or something else (hilariously, I've seen someone use their allergies to try and micromanage what everyone else around them can eat, down to how their spouse's coffee is brewed).
https://www.psychologytoday.com/us/blog/eating-disorders-the...
https://www.livescience.com/64423-food-allergies-overestimat...
https://www.aafp.org/pubs/afp/issues/2008/0615/p1678.html
https://www.verywellhealth.com/fake-food-allergies-1323997
https://www.cosmopolitan.com/food-cocktails/a5402/food-aller...