Heartburn Free contains an all-natural key ingredient, D-limonene, which is the main component in the citrus peel oil of oranges. It is isolated from the citrus peel oil by a purification process. Despite this purification, Heartburn Free may contain minute amounts of substances problematic to allergic individuals. Thus, citrus allergies could possibly be aggravated by exposure to this product. We cannot completely predict individual responses to any dietary supplement, as reactions may vary based on unique health and nutrition needs. Therefore, we encourage consumers to discuss all substances they are considering for use with their allergy specialist if they suspect a product may cause an allergic reaction.