Which component of a local anesthetic is most likely to elicit an allergic response?

The component of a local anesthetic most likely to elicit an allergic response is sodium bisulfate. This is because sodium bisulfate is commonly used as a preservative in certain anesthetic formulations, especially in solutions that contain epinephrine. Allergic reactions to sulfites, such as sodium bisulfate, are recognized and can occur in sensitive individuals.

While lidocaine, epinephrine, and sodium chloride can cause adverse reactions, these are generally not classified as true allergic responses in a significant number of patients. Lidocaine is a widely used local anesthetic with a low incidence of true allergy. Epinephrine, while it can cause side effects such as anxiety or increased heart rate, is not associated with allergic reactions in the typical use of local anesthetics. Sodium chloride is simply a buffering agent and would not invoke an immune response.

In summary, sodium bisulfate is the preservative that can provoke allergic reactions in some individuals, making it the most likely component among those listed to elicit such a response.