I get one or two big pimples above my upper lip every few months. i do not have acne anywhere else. how can i prevent these?

Staph infection? : Some people get colonized with staphylococcus in the nose, and sometimes will have a small outbreak in the area under their nose, especially after colds. If you're having frequent "pimples" they may be small boils that resolve spontaneously. Getting a prescription ointment and putting a small amount in the front of the nose with a q-tip can help eradicate this carrier state.

Herpes simplex?: If these are painful and recur in the same place, they are probably herpes simplex. Your physician knows of medicine that can stop them.