At the same time, cortisol stimulates the overproduction of sebum, the oil that is implicated in acne. “So for many of us, our skin seems more oily when we’re under stress, and it’s more acne prone,” she said.
All of this alters the skin’s pH, which compromises the acid mantle and creates an inhospitable environment for the one trillion symbiotic micro-organisms that exist on and in the skin barrier — a.k.a., the microbiome.
Under ideal conditions, the microbiome renders topical skin care all but superfluous. There are microbes that feed off sebum, which helps sustain healthy oil levels. There are microbes that feed off dead skin cells — the original exfoliators! There are microbes that produce peptides and ceramides, two buzzed-about beauty ingredients that keep skin firm and moisturized. There are microbes that offer protection from pollution, sunlight and invading pathogens.
“If you’re not producing enough of those healthy fats and not maintaining a healthy barrier, though, you’re altering the terrain on which these microbes grow and thrive,” Dr. Bowe said. “Imagine stripping the soil of all the nutrients and seeing if your vegetable garden is going to grow. It’s the same for the skin.”
In turn, the microbiome may experience an overgrowth of so-called bad bacteria (like C. acnes, the strain associated with acne) and a dearth of good bacteria. The microbiome becomes more prone to infection, irritation, inflammation and hyperpigmentation. It becomes more sensitive to outside aggressors, like the free radicals generated by pollution.
Stress prompts the body to produce internal free radicals, as well. “You can think of free radicals like little missiles,” Dr. Bowe said, in that they target cells for destruction and cause oxidative stress. When free radicals target DNA, it leads to skin cancer. When free radicals target elastin and collagen, it leads to fine lines and wrinkles. When free radicals target lipids, it leads to dehydration and skin barrier damage and acne.