Now, and this goes back to what was just discussed with the reproofing, you will need to wash your new running jacket regularly. The primary reason, other than doing so for cleanliness and to eliminate odors, is that dirt and dust can affect the shell’s performance to repel water. So, the quicker you rid the shell of dirt and dust, the better. In regard to how often this should be, if you notice bad odors, noticeable dirt, or the performance weakening, it is time to wash it.