Allergy symptoms refer to the physical reactions that occur when a person is exposed to an allergen, which triggers their immune system to produce an overreaction. These symptoms can vary from mild to severe and may include sneezing, runny nose, itchy eyes or skin, rashes, hives, coughing, wheezing, difficulty breathing, swelling of the face or throat, nausea, vomiting, diarrhea, dizziness, lightheadedness and in some cases, anaphylaxis which can be life-threatening. The specific symptoms experienced depend on the type of allergy a person has - for example, food allergies may cause gastrointestinal issues while environmental allergens such as pollen or pet dander might trigger respiratory problems.