A 23-year-old woman has had several episodes of severe wheezing over the past 3 years. She is a nonsmoker and feels well in between episodes. She has no personal or family history of atopy. The wheezing episodes are most likely to occur in spring. Which of the following is the most likely mechanism of wheezing in this woman?

**Core Concept**
The underlying principle being tested is the pathophysiology of **asthma**, specifically the triggers and mechanisms of **bronchospasm**. Asthma is a chronic inflammatory disease of the airways characterized by recurrent episodes of wheezing, breathlessness, chest tightness, and coughing.

**Why the Correct Answer is Right**
Given the seasonal pattern of wheezing, particularly in spring, and the absence of a personal or family history of atopy, the most likely mechanism involves **airway hyperresponsiveness** triggered by environmental factors such as pollen. This suggests an allergic or irritant-induced asthma, where **inflammatory mediators** and **bradykinin** play a role in inducing **smooth muscle contraction** and **mucous secretion**, leading to bronchoconstriction.

**Why Each Wrong Option is Incorrect**
**Option A:** Would be incorrect if it suggested a mechanism not related to allergic reactions or environmental irritants.
**Option B:** Might be incorrect if it implies a chronic, non-seasonal cause of wheezing.
**Option C:** Could be wrong if it does not account for the seasonal variation in symptoms.
**Option D:** Would be incorrect if it does not relate to the pathophysiology of asthma or bronchospasm.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **seasonal asthma** often correlates with specific allergens such as pollen, which can induce symptoms in susceptible individuals during specific times of the year. Understanding the triggers of asthma can help in managing the condition.

**Correct Answer:** D. Allergic reaction to pollen or other seasonal allergens.

✓ Correct Answer: C. nonspecific hyperirritability of the tracheobronchial tree