How common is herpes 1? and if you get cold sores does that mean you have herpes 1 and will it show up on a blood test?

Oral herpes: Herpes simplex virus type 1 (HSV1) infection is extremely common; up to half of all people in the US have it. Most infections cause few or no symptoms, but many get recurrent oral herpes ("cold sores", usually blister- or pimple-like, usually on lips, around nose, etc). Canker sores in the mouth are not cold sores and not herpes. A blood test can detect HSV1, but it's not perfect -- misses 30%.