**Core Concept**
H1 blockers, also known as antihistamines, are a class of medications used to treat allergic reactions by blocking histamine receptors. Sedation is a common side effect of many H1 blockers due to their action on the central nervous system.

**Why the Correct Answer is Right**
The correct answer is **C. Fexofenadine**. Fexofenadine is a non-sedating H1 blocker that works by selectively blocking histamine H1 receptors without crossing the blood-brain barrier, thereby minimizing its sedative effects. This is in contrast to older H1 blockers like diphenhydramine, which can cause significant sedation.

**Why Each Wrong Option is Incorrect**
**Option A:** **Diphenhydramine** is a classic sedating H1 blocker that can cause significant drowsiness and is often used as an antihistamine in over-the-counter sleep aids.
**Option B:** **Chlorpheniramine** is another older H1 blocker that can cause sedation and is often used in combination with decongestants in over-the-counter cold medications.
**Option D:** **Triprolidine** is an H1 blocker that can cause sedation and is often used in combination with decongestants in over-the-counter cold medications.

**Clinical Pearl / High-Yield Fact**
When choosing an H1 blocker, it's essential to consider the patient's age and medical conditions, as older adults and patients with certain medical conditions may be more susceptible to sedation.

**Correct Answer: C. Fexofenadine**