**Core Concept**
Local anesthetics work by inhibiting the sodium channels in nerve cells, preventing the initiation and transmission of nerve impulses. This results in a temporary loss of sensation in the area where the local anesthetic is applied. However, some local anesthetics may cause allergic reactions due to their chemical structure, which can trigger an immune response.

**Why the Correct Answer is Right**
The correct answer is **C. Procaine**. Procaine is a local anesthetic that is more likely to cause allergic reactions due to its ester linkage, which is metabolized to para-aminobenzoic acid (PABA). PABA is a known allergen that can trigger an allergic response in some individuals. This is in contrast to other local anesthetics like lidocaine and bupivacaine, which have an amide linkage and are less likely to cause allergic reactions.

**Why Each Wrong Option is Incorrect**
**Option A:** **Lidocaine** is an amide-linked local anesthetic and is not typically associated with allergic reactions. **Option B:** **Bupivacaine** is another amide-linked local anesthetic and is also less likely to cause allergic reactions. **Option D:** **Articaine** is an ester-linked local anesthetic, but it is not as commonly associated with allergic reactions as procaine.

**Clinical Pearl / High-Yield Fact**
When choosing a local anesthetic, it's essential to consider the patient's history of allergies and sensitivities. Esters, like procaine, are more likely to cause allergic reactions, whereas amides are generally safer.

**Correct Answer:** C. Procaine.