Encontre la respuesta que buscaba en otro thred
"Why can't I get my hair wet for four hours after using Rogaine / Can I use Rogaine after showering with my hair wet?
Wet scalp skin increases the penetration of topical drugs by several times (2x-5x more powerful). Because Rogaine does have side effects, they must attempt to keep you from increasing its potency and thereby side effects. However, if you apply Rogaine and do not experience any side effects, you might try applying it to wet scalp if you want to make it more potent. Be sure you have someone around if you do this since there is a change that you may not experience side effects on dry scalp, but may with wet scalp. If you experience side effects when applying Rogaine to dry hair, DEFINITELY *NEVER* apply it to your hair wet and be sure to follow Upjohn's instructions about not letting your hair get wet for 4 hours.
From personal experiences, I have heard many people who have said that Minoxidil did not work well for them, but after they started applying it to a wet scalp, it started working much better."