Which term describes allergic reaction development?

• A. Sensitization
• B. Acute toxicity
• C. Chronic toxicity
• D. Systemic toxicity

Answer: (A)

Allergic reaction development is described by sensitization. After the first exposure to an allergen, the immune system becomes primed, producing specific antibodies (often IgE). Those antibodies stay ready, so when the substance is encountered again, the body responds with an allergic reaction—releasing histamines and other mediators that cause symptoms such as itching, hives, or wheeze. This is different from toxic effects: acute toxicity is immediate harm from a single exposure, chronic toxicity is harm from long-term exposure, and systemic toxicity refers to effects that affect the whole body. So sensitization best explains how an allergic reaction develops.