If you are prepping your skin for an injection at home, apply a small amount of the chlorhexidine solution to a cotton pad and swipe it over the skin area where you'll administer the injection.
Pediatr Infect Dis J. 2006;25(8):665-675. In summary, after topical applications of chlorhexidine, some percutaneous absorption occurs, particularly in preterm newborns, but only at trace levels.