The World's Foremost Expert On Skin Longevity Says This Is The First Sign Of Aging

Ask someone what the first signs of skin aging are, and you'll likely hear the usual suspects: crow's feet, forehead lines, maybe a sun spot or two. We've been conditioned to think of aging as something that shows up in the mirror—visible, measurable, and (ideally) treatable with the right serum.

But according to Saranya Wyles, M.D., Ph.D., director of the Regenerative Dermatology & Skin Longevity Laboratory at Mayo Clinic, we've been looking at this all wrong. During her conversation with mindbodygreen co-founder Jason Wachob at the 2026 Revitalize summit, she explained that the earliest sign is one you feel: Hydration loss. 

Here's the thing: Wrinkles and sagging don't just appear out of nowhere. They're the downstream result of changes that have been happening beneath the surface for years.

“The minute we start aging, our barrier, which is like a basket weave, slowly starts to open up. So that means, just at rest, you’re losing water a lot easier,” she says. 

Let’s get into why. Wyles uses a helpful analogy: "There's the epidermis, dermis, and the hypodermis. There are multiple different layers that go into how the skin changes."

The stratum corneum, the thin layer of dead skin cells that’s in the epidermis, is the outermost part and its job is to keep moisture in and environmental stressors out. But all that hard work takes its toll. 

Over time, the lipids that hold this “basket weave” structure together begin to break down and become less organized, making it easier for water to escape. This is where things start to accelerate. As water escapes more easily, the skin becomes drier and more fragile, which can further impair barrier function. Eventually, this leads to structural changes in the dermis, including collagen loss.

"So you actually start seeing a decline in your skin health and that collagen matrix early, at the age of 20," Wyles shared.

Transepidermal water loss, or TEWL, is exactly what it sounds like: the process by which water evaporates from your skin into the environment. A healthy barrier keeps this loss to a minimum. But as we age, the barrier becomes less efficient at holding onto moisture.

Research supports this: One study1 found that older adults had significantly higher baseline TEWL rates compared to younger subjects. Even more telling was that when the barrier was disrupted, older skin took roughly twice as long to recover.

Other research shows that the ceramides in our stratum corneum—the lipids that help hold the barrier together—also shift with age2, moving toward shorter chain lengths that are associated with barrier function decline.

If the first sign of skin aging is hydration loss—not wrinkles—then it follows that the first priority should be barrier support, not anti-wrinkle treatments.

This is actually good news. It means you don't have to wait until lines appear to start taking care of your skin in a meaningful way. And it shifts the conversation from correction (fixing what's already happened) to prevention (protecting what you've got).

As Wyles puts it: "So you start noticing drier, itchy skin. So pay attention to those, because that's your skin telling you it needs that barrier support."

Think of it this way: You wouldn't wait until your muscles have atrophied to start exercising. The same logic applies to your skin. Supporting your barrier function early—before the visible signs of aging appear—is one of the most proactive things you can do for long-term skin health.

Ready to put this into practice? The gist is pretty simple: Even starting in your early 20s, flood your skin with hydration, keep a consistent skin care practice (that includes SPF), avoid the urge to exfoliate your skin into oblivion, and prioritize eating a nutrient-dense diet, chock full of amino acids, healthy fats, and antioxidants. That’ll put you on a good path for glowing skin for years to come. 

But in case you’re looking for more specific advice, here’s a breakdown: :