An allergy is an intolerance to a particular substance. Some people have extreme allergic reactions which would require medical attention, however many people have less, but still significant reactions because they are becoming more intolerant to the food, substance or environment. If you think you may have allergies, but you are unclear what they are, nutrition can help restore the underlying immune system and/or digestive imbalances that will provoke an attack. Generally dietary interventions can help to restore the issue, however in some cases diagnostic tests may be considered.