What is the term for a foreign substance that causes an allergic reaction?

The term for a foreign substance that causes an allergic reaction is "allergen." Allergens trigger the immune system to respond, often resulting in symptoms such as sneezing, itching, or swelling. Common examples of allergens include pollen, pet dander, certain foods, and insect stings. When the body encounters an allergen, it may produce antibodies, specifically immunoglobulin E (IgE), which then lead to the release of chemicals like histamine that contribute to the allergic response.

Understanding this terminology is important for EMTs, as recognizing allergens plays a critical role in assessing and treating patients with allergic reactions. Other substances, like histamine or leukotrienes, are involved in the body's response to allergens but are not the allergens themselves. Histamine is a chemical released during an allergic reaction, and leukotrienes are inflammatory chemicals that can exacerbate allergic symptoms. Antibodies, on the other hand, are proteins made by the immune system to identify and neutralize foreign objects like allergens, but they don't represent the foreign substance itself. Thus, "allergen" is the most accurate term for describing a substance that provokes an allergic reaction.