When you wear makeup while you sleep, you hinder the skin's natural renewal process. Soon enough, the skin stops breathing and the first signs of fatigue appear. Powder-based products usually help keep the skin dry, but at night they can dry it out even more and mix with the oils released by the skin. This can cause the skin to flake and become even oilier in some areas, which can lead to combination skin, not to mention that this can increase the risk of developing inflamed acne.
A lot of makeup focuses on the eyes, but the human eye is also one of the most important and sensitive parts of the body. During sleep, improperly removed makeup can irritate and itch the eyes, causing serious infections. Always remove waterproof mascara as best you can!
Since most makeup is oily or mineral-based, it may clog pores overnight and causes more acne breakouts. Also, makeup residue and the ingredients it contains can cause various skin blemishes if left on all night, or even cause inflammation or allergic reactions that lead to developing a more sensitive skin. Therefore, it's important to remove your makeup before going to bed and moisturize your skin afterwards so that it can breathe.