But the changes in our skin go far beyond environmental exposure and sensorial preferences. Recently I was talking to skin care expert and naturopathic doctor Trevor Cates, N.D., on my podcast Clean Beauty School, and she shared that our hormones actually change throughout the year—which could result in changes in the skin too. One study she references was about the shift from winter to spring: The “winter-spring” peak, as they call it, is a time when humans and most other animals experience a surge in hormone activity, which results in “a physiological peak in basic human functions.” For example, during this time individuals often see a surge of estrogen. Estrogen is a sex hormone known for many things, including several skin benefits including increased collagen production, hydration, and elasticity. She also references the effects of seasonal changes on the circadian rhythm. Seasonal changes in sun exposure can affect how we sleep, which influence what hormones are released in sleep. Why does this matter for your complexion? Skin can enter repair mode when you’re resting, largely thanks to melatonin. What should be done about this? Well, seasonal changes are part of life, of course. But being aware of the effects they may be having on your body and skin can help you make better choices. For example, if your skin is looking a little sallow in the winter, when you are experiencing more cortisol and less estrogen, you may invest in collagen-supporting topicals like vitamin C serums. And during the spring and summer months, when your skin is feeling its best, you can forgo heavier products and let your natural complexion shine.