Source: Natural Society, by Mike Barrett
Gluten sensitivity, for example, is often mistaken for a food allergy
More Americans claim to have food allergies than ever before, but a report published in 2016 from the National Academy of Sciences says that it’s hard to know how many people in the U.S. actually have food allergies. Although many healthcare professionals involved in patient care agree that an increase has occurred, specifying its actual extent is complicated by factors such as inconsistent data or studies that use variable methods.
Part of the problem is that many people self-diagnose and can easily misinterpret their symptoms. Food allergies can be mistaken for gluten sensitivity or lactose intolerance, e.g., neither of which fits the medical definition of an allergy. 
Dr. Virginia Stallings, a board-certified nutrition pediatrician at the Children’s Hospital of Philadelphia and the chair of the committee that wrote the report, said:
“There are a lot of misconceptions about what a food allergy is.”
One of the ways in which a misinterpretation arises is when parents introduce milk or another new food into their child’s diet, and then see that the child has an upset stomach or other gastrointestinal symptoms. These symptoms could indicate lactose intolerance, but the parents may suspect a food allergy. In reality, food intolerance and food allergy are two different conditions.
“The reason food allergy symptoms are often confused with other [conditions] such as lactose intolerance is because there’s an overlap in some of the symptoms.”
The panel estimated that about 5% of U.S. children have legitimate food allergies, and wrote that:
“Eight food groups are considered to be major allergens. These are milk, egg, peanut, tree nuts, wheat, soy, fish, and crustacean shellfish.” 
“Questions persist about whether food allergy prevalence has been on the rise within the past two decades and why. The current data do not unequivocally support the occurrence of such a rise.”
The Definition Of A Food Allergy
Allergies are caused by an immune response to a normally-harmless food or other substance. Allergies typically cause hives and swelling or gastrointestinal distress. Severe food allergies can be life-threatening. In contrast, someone with lactose intolerance can’t easily digest the natural sugar in milk, and the condition is not life-threatening – just highly uncomfortable. 
As the American Academy of Pediatrics points out, “while lactose intolerance can cause a great deal of discomfort, it will not produce a life-threatening reaction such as anaphylaxis.” 
Anaphylaxis (severe allergic reaction) can cause someone to go into shock within seconds or minutes of contact with the food or substance (latex, e.g.) that he or she is allergic to. A sudden drop in blood pressure occurs; and the airways narrow, which blocks normal breathing. Other symptoms of anaphylactic shock can include a rapid, weak pulse a skin rash, and nausea and vomiting.