When you wash your face with lukewarm water instead of cold, you raise the skin's temperature slightly, causing blood vessels and pores to dilate in an effort to cool you down. Space between the cells (where the hyaluronic acid lives) means there's a greater surface area for absorption, which helps your products to get in. Says dermatologist Heidi Waldorf.
PLUS, ingredients move through skin and interact with cells more quickly when the skin is warm. Says David Bank, a professor of dermatology at Columbia University/New York-Presbyterian Hospital.
P.S. Apply toner, serum, moisturizer and or face oil as soon as you get out of the shower or bathtub! If you wait, skin starts losing water vapor, which means less product absorption and drier skin!