It will increase the hygiene needs.
It will remove all makeup (except for face painting) of your sim!
You can re-apply the makeup by selecting ‘Apply Makeup Again’ menu on your sim.
It gives your sim an Energized +1 moodlet! This moodlet will last for 1 hour and 30 minutes!
If you have KawaiiStacie’s ‘Slice of Life’ mod, washing face will prevent acnes!
Washing face once will not completely make your sim immune. Instead, your sim will have to wash their face consistently, on a daily basis!