To completely dry, an hour or so.
A great trick is to wipe the residue from the outside of the tip before applying. This will help it get to your scalp and not your hair. What I do is use the applicator as a "pen" and draw zig-zags across my scalp. I don't massage it in since the applicator has already spread it around for me. This really keeps my hair dry and keeps the medicine on my scalp where it is supposed to be. I usually apply mine, brush my teeth, shave, get dressed and by that time, maybe 15 minutes later it's ready to be styled.