How do you tell the difference between folliculitis and genital herpes?

Doctor can evaluate. Folliculitis usually affects a larger area of skin than the small spot that a herpes sore affects. Folliculitis is tiny pustules where the hair follicles are. Herpes makes tiny blisters, in a cluster, very close together. Herpes blisters (vesicles) break open with some clear or yellowish fluid, not pus like in folliculitis. A doctor can evaluate and tell the difference.
Location. Genital herpes usually on penis, scrotum, vulva, pubic area or sometimes, groin. They are small grouped blisters. Folliculitis, by definition, developed around hair follicles. So it can be on body, face, arms, legs, etc. It rarely appears in genitalia unless there are hairy and thus having follicles. Besides, they are pustular, red bumps.