Which type of substances can cause an allergic reaction after repeated exposure?

The correct answer identifies sensitizers as substances that can cause an allergic reaction after repeated exposure. Sensitizers are specific types of chemicals that, when introduced to the body, may not cause an immediate reaction. However, with continued exposure, they can lead to an immune response, resulting in an allergic reaction upon subsequent exposures. This increasingly reactive state often stems from the immune system’s adaptation to the presence of these substances, leading to sensitivity.

For context, corrosives are substances that can cause destruction of living tissue or severe corrosion of material. They function through direct chemical action rather than through an immune-mediated response, which is characteristic of sensitizers. Mutagens are agents that can cause changes to DNA, potentially leading to cancer or other genetic issues, but they do not specifically elicit allergic reactions. Pathogens, which include bacteria and viruses, cause infections rather than allergic reactions. Therefore, among these options, sensitizers are uniquely defined by their ability to lead to allergic reactions upon repeated exposure.