Allergy is a hypersensitivity disorder related to the immune system. In case of allergy, the body reacts to the otherwise not harmful substances. People with allergies are generally sensitive to more than one substance. Any such substance potential of causing an allergy is known as an allergen. Allergy is a type I hypersensitivity reaction which is immunologic in nature; occurring after the intake of an allergen by the patient. It can be a systematic or localized reaction depending on the allergen involved. Allergy caused due to lemon can be from ingesting a lemon, cooking with lemon or lemon coming in contact with your skin. The symptoms of lemon allergy include watery eyes, rashes around the mouth, vomiting and asthmatic symptoms. The IgE allergy test helps to determine if you are allergic to lemon or any other citrus fruit.