What to do if I have rash on face after using vigamox eye drops?

Stop it. If you developed rash it means you may have allergy to the drop. Please notify your doctor. Your doctor will give you a different antibiotic.
Possible. topical allergy is possible or it may not be to vigamox at all. Typical of an allergic reaction is significant itch to the rash. One eye or both? The eyelids usually are swollen and very itchy. Of course stopping the drops helps but your doctor should be able to give an ointment to sop the itch and the swelling.