What is responsible for allergic reactions in ester anesthetics?

In ester anesthetics, allergic reactions are primarily associated with para-amino benzoic acid (PABA), which is a metabolite of these agents. When ester local anesthetics are metabolized in the body, they break down into several components, one of which is PABA. This compound can trigger allergic responses in some individuals, leading to symptoms such as rashes, itching, or more severe reactions.

The parent compound does not typically provoke an immune response that results in allergic reactions, as the ester itself is usually broken down before it can cause such effects. Pseudocholinesterase is an enzyme involved in the metabolism of some ester anesthetics but is not the direct cause of allergic reactions. Sodium bisulfite is often added as a preservative in local anesthetics but is more commonly associated with sulfite allergies rather than direct reactions to ester anesthetics themselves. Therefore, the specific connection between PABA and allergic reactions is what makes it the correct answer.