I kissed a guy friday at noon and then saturday afternoon my lip is swollen on the left side and has bumps. is it herpes or an allergic reaction?

Allergic to a kiss?: A picture would certainly help us here please, since there are thousands of reasons for lip swelling. Sorry, but it would be inaccurate at best to hazard a guess as to your cause at this point.

Very early: For HSV 1 it would be very early; incubation time is between 2 and 12 days with a peak between 3 and 6 days. Since many people catch the HSV-1 infection in early infancy this could be a flare-up of pre-existing HSV-1 exposure.