Does the local numbing injection they use to remove cyst cause any possible side effects?

If you are allergic, it can cause an allergic reaction-either a local or systemic reaction. Other than that, it can cause local irritation but it doesn’t cause any systemic reaction since it is not going into a blood vessel and then going throughout the body. One possible side effect is local infection since a needle is used but alcohol is used first to decrease this possibility. Good luck!