What term describes an allergic reaction created by repeated exposure to a chemical or substance?

The term that describes an allergic reaction created by repeated exposure to a chemical or substance is sensitization. This process occurs when the immune system becomes increasingly reactive to a substance after multiple exposures. Initially, the first encounter with the allergen may not produce any noticeable symptoms, but subsequent exposures can lead to an allergic response as the immune system recognizes the substance as a threat.

In contrast, "sensitivity" is a broader term and may refer to a range of reactions to various stimuli, not necessarily limited to allergic responses. "Allergy" is a general term for an adverse immune response, but it does not specifically imply the repeated exposure aspect. "Intolerance," on the other hand, typically refers to a non-immune reaction and different mechanisms, such as metabolic or digestive issues. Thus, sensitization is the most precise term for the scenario described.