I went for threading upper lips twice last year. Each time also got tiny bumps after the threading. I think because the hair have been removed and results in the pore got some bacteria infection, but the break out will only for a short period of time.

The bigger problem is the hair will grow back more. Previously, only 1 side of my upper lip is more hair, while another side is lesser hair, now after 2 times threading, both side is equal hair. I won't do anymore threading for upper lips.