Anesthetic allergy

Typically speaking, anesthetic allergies are extremely rare (although adverse reactions to lidocaine are not at all rare). However, because most "underground practitioners" are working without the support of resuscitation equipment, it should still be taken very seriously.

In addition, it's often not actually the anesthetic itself that's being reacted to—there are many other active compounds in the solution. It could just as easily be a reaction to the preservative methylparaben (chemically similar to paraminobenzoic acid), or to the metabisulfite (which you'll find in anesthetic solutions with epinephrine).