Too cold, and your pores slam shut, trapping the very dirt and bacteria you are trying to wash away. Hot water dehydrates skin and creates a blotchy and red appearance. Warm water will open up pores without inflammation.Luminescent Serum Only wash with warm water to soothe skin. Too cold, and your pores slam shut, trapping the very dirt and bacteria you are trying to wash away. Water that is too hot may leave your face red and blotchy.