Food allergies occur when the immune system mistakenly identifies certain foods as harmful and triggers an allergic reaction. Common signs of a food allergy include hives, swelling of the face or throat, vomiting, diarrhea, and dizziness. Food allergies are diagnosed through a patient's medical history, skin prick tests, blood tests to detect IgE antibodies, and elimination diets that identify the specific foods causing reactions. Treatment involves strict avoidance of the offending foods and having epinephrine available in case of a severe allergic reaction known as anaphylaxis.