It is also advisable for you to avoid using this oil on your scalp while the hair is wet, as it can cause damage to the hair ends. In addition, the essential oil of patchouli can take longer for treatment effectiveness to be noticed compared to other plants and herbs due to its slow onset of action. If left untreated, patchouli oil for hair will not work as intended. Regular use would require about a week for full results to show up, which means it is not suitable as a quick-fix remedy. It may be advisable to alternate between two different recipes once every few days before taking up another one.