“Dietary Restriction” is the blanket term for any reason why a person cannot eat a particular food. There are many kinds of dietary restrictions in our world. You already know about food allergies, but what about intolerances, celiac disease, and preferences?
Unlike food allergies, an intolerance to a food is based in the digestive tract and does not involve the immune system. An intolerance usually means that the person lacks the proper enzymes needed to digest a specific protein. The symptoms of a food intolerance include vomiting, stomach pain, and diarrhea. Since this kind of reaction can take longer to occur after eating a food and may last for longer, they are harder to diagnose. The best treatment for this kind of dietary restriction is avoiding of the food. For some intolerances, you can take the enzyme needed to absorb the protein (ie lactaid for the lactose intolerant) before eating a food with that protein, and have no problems. Epinephrine will not help in this kind of situation.
Celiac Disease is an auto-immune disease that affects 1 in 100 people worldwide. When someone with celiac disease ingests gluten, their immune system triggers an attack to the villi in the small intestine. As these villi get damages, the body becomes unable to absorb nutrients. This can lead to several other autoimmune disorders if left untreated. The symptoms of celiac disease include the symptoms of an intolerance and weight loss, delayed puberty, behavioral disorders, and fatigue. Celiac Disease is hereditary and occurs in 1 in 10 people who have a parent, sibling, or child with celiac. The only treatment for celiac disease is avoiding foods that contain gluten.
Most other dietary restrictions fall under the umbrella of preferences. Some preferences are due to religious reasons, such as a Kosher diet for Jewish people, halal for Muslims, and vegetarian for Hindus. Other people make choices to follow specific diets (vegan, vegetarian, pescatarian, paleo, organic) for ethical reasons. Some people follow various types of restrictive diets for weight loss purposes. And other preferences are just due to people who do not like a specific food just for its taste. While all preferences have valid reasons, it is important to not call these preferences an “allergy” when dining out. Although people with preferences want to avoid a specific food, accidental exposure to that food will not cause them any medical consequences. When you state that you have an allergy at most restaurants, there is a procedure that all the kitchen staff will follow to ensure that no cross contact occurs and you do not want them to have to go through all of that just because you like your hamburgers without cheese.