Why Doesn't The Lidocaine At This Doc's Office Work?

I respond perfectly to Lidocaine. It kills 100% of the pain for all other dental and skin procedures. However, in this one dermatologist's office, my mole removals are 100% horribly painful. The lidocaine does not work one bit! He tells me it does not work on me because I am allergic to sulfa drugs. I can find no medical literature to support this. I often hear other patients cry out when waiting for my appointment. A charming doc, but is he possibly sadistic? Is he using expired lido?