Peanuts, tree nuts, milk, eggs, wheat, soy, fish and shellfish are the foods that cause the most allergic reactions, explains Food Allergy Research and Education. Only around 5 percent of children and 4 percent of adults are truly allergic to certain foods, although many more suffer dietary intolerance, states WebMD.
Sneezing; a stuffy or runny nose; itchy, watery eyes; swelling; a rash; stomach cramps; and diarrhea indicate a mild allergy, according to Healthline. Difficulty breathing; swelling of the lips, tongue or throat; hives; dizziness or fainting; and nausea or vomiting point to a more serious allergy.
In fish allergies, WebMD points out many people are severely allergic to fresh salmon, tuna and halibut, and being allergic to one kind of fish means a person might turn out to be allergic to other kinds too. The same is true for nuts and shellfish.