The Scientist: Claudia Aguirre, Ph.D., a neuroscientist working in the skincare industry

The Answer: Your body is wired for “fight or flight.” When our caveman ancestors encountered danger, a flood of stress hormones prepped their bodies to do battle or hightail it to safety. The same neurochemistry is at work today, but you can’t run away from an angry boss—or punch her in the face—so the stress hormones go at their business in new, and unfortunately less productive ways.

Stress kicks off a chain reaction, starting with the release of corticotropic releasing hormone (CRH) in the brain. From there, CRH triggers corticotropin, which stimulates the release of cortisol, the main hormone associated with stress. Now you’ve got all these stress hormones amassing in your body, preparing to help you escape from danger. But you’re at your desk, or stuck in traffic, or otherwise sitting on your duff, so the hormones end up doing more harm than good.

They cause inflammation all over the body, suppress the immune system, and bind to specific binding sites on cells in the skin that produce oil, or sebum, which gets the sebaceous glands pumping. (Why our skin gets oily in response to stress is an unsolved mystery of evolution.) The excess oil clogs up inflamed pores, and acne causing bacteria—that your immune system isn’t up to killing off—collect inside.

Result: Acne.

This can all happen within a couple days of being seriously stressed out. To combat the pimply effects, it’s important to drink extra water, because psychological stress dehydrates the skin. Meanwhile, you want to blot generously to sop up the excess oil on your face, or apply a clay mask to clear clogged pores. You can help prevent a nasty breakout by pretreating with salicylic acid, which reduces inflammation and gently exfoliates skin. If a zit crops up, spot treat with a product that contains benzoyl peroxide, sulfur or salicylic acid.

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