Allergies are a reaction your body has when exposed to proteins in certain plants, animals, food, etc.
Food allergy cause: when your immune system mistakes a certain protein in a food as harmful. Your body triggers cells to release chemicals that try to neutralize the food, the next time they eat the food, they will have an allergic reaction.
Seasonal allergy cause: Exposure to pollen is often what causes seasonal allergies.
Some common symptoms are itchy and watery eyes, sneezing, irritated nose, headache, fatigue, sore throat, coughing, itching in the mouth, hives or eczema, swelling, trouble breathing, abdominal pain, dizziness, lightheaded, or fainting.