The prevalence of food and environmental allergies has skyrocketed in the last couple of decades. This is the result of over sanitary living environments and lack of exposure to outdoor allergens from plants and animals as children. This is compounded by the fact that each subsequent generation is made of weaker constitution and overall more of a whiny type. Go back 30-40 years and you won't see human beings dying or becoming deathly ill from all pervasive ingredients like gluten, dairy, nuts, etc.
If you have serious medical allergies, do not complain about public transportation not bending over backward to suit you. I find it incredibly generous they have so many options for meals in flight and I have seen them cater towards allergies numerous times.
There is a point at which they cannot prevent some degree of cross contamination as I'm sure they don't wash hands or change gloves every time before they touch someone's tray or cup.
Pack your own food if you have serious food allergies or fly private.