What is meant by "sensitization"?

Sensitization refers to the process whereby an individual develops an increased sensitivity to a substance after their initial exposure to it. In the context of exposure to pesticides or other chemicals, this means that upon first contact, a person may not exhibit any noticeable reaction, but with subsequent exposures, they can become more sensitive, leading to allergic reactions or other negative responses.

This can occur as the immune system recognizes the substance and starts to react to it as a potential threat, creating memory cells that respond more vigorously to future exposures. This phenomenon highlights the need for careful handling and consideration of repeated exposure to certain chemicals, as it can lead to increased health risks over time.

The other options do not capture the essence of sensitization correctly. Reaction to familiar allergens may indicate existing allergies, increased tolerance to a substance refers to a reduced reaction over time, and immediate allergic reactions are separate from the prolonged process of sensitization. Understanding sensitization is crucial for anyone working with pesticides, as it underscores the importance of protecting oneself from repeated exposure.