Well + Good posted "Why pores seem to grow in size over the course of the day" featuring Dr. Purvisha Patel.
The article includes Dr. Patel's expert commentary on skin pores.
Pores are among the most confounding things on the planet (right alongside quantum physics and taxes). Can you really shrink them, or not so much? How do you get those stubborn blackheads out? Why are they always accumulating gunk?
While reading a Reddit skin-care thread, one user posed yet another question about those teeny holes in your skin: Why do your pores seemingly get larger by the afternoon, yet smaller when you wake up? Cue that thinking face emoji. I’ve noticed it to be true—I wake up with a pretty calm, smooth complexion, but things just get out of control as the hours roll by. Why?
As it happens, pores aren’t exactly changing in size at all—but the illusion happens for a biological reason. “Pores don’t actually physically change size, but they may look bigger as they accumulate oil throughout the day,” says Purvisha Patel, MD, a board-certified dermatologist and founder of Visha Skincare. “They tend to look bigger when exposed to heat or steamy conditions and shrink with cold conditions, but they do not grow.”
Essentially, the oil glands accumulate sebum, which then makes the pore’s appearance change—hence the common confusion. You can combat seemingly large pores, though. “Good oil-busting exfoliating cleaners such as Visha Skincare Advanced Purifying Cleanser can help,” says Dr. Patel. “Salicylic acid, glycolic acid, lactic acid, tea tree oil, and zinc help exfoliate the tops of pores and shrink the oil production, making them stay small throughout the day.”