Sea fennel and mushrooms in skincare: why Prep is retinol-free

People ask us all the time: if Prep doesn't have retinol, what's doing the work on texture?

The short answer is a complex made from sea fennel and two mushrooms, shiitake and turkey tail. Here's what they are, what the science says, and why we built Prep without retinol.

Why no retinol

Retinoids have more clinical evidence behind them than almost anything in skincare. We're not going to pretend otherwise.

But they come with a ramp-up: weeks of dryness, peeling and sensitivity while skin adjusts. For skin in hormonal change, which is often already drier, thinner and more reactive, that adjustment period can be the hardest part. We wanted a first step that works with your skin from the first day. So Prep is retinol-free, with no ramp-up.

That doesn't make sea fennel "plant retinol." It isn't, and no one has shown it works the same way. It's a different ingredient doing a different job.

Sea fennel: a plant that lives on salt

Crithmum maritimum, also called rock samphire, grows on sea cliffs and rocky shores, in salt spray and full sun. It's a halophyte, a plant built to survive salty soil.¹ Plants that live under that kind of stress tend to be rich in protective compounds, and sea fennel is no exception: it's full of phenolics, mainly chlorogenic acid, which show strong antioxidant activity in lab tests.²

The renewal research is early and all in the lab. In one 2025 study, a chlorogenic-acid-rich sea fennel extract helped a lab-grown skin model rebuild its outer layer after UV stress.³ A 2025 review of 79 studies on the plant concluded that studies in living systems are still limited.⁴

So we describe it for what it does in a formula: Prep smooths the look of texture.

Mushrooms: shiitake and turkey tail

Mushrooms are on the table most days in both our homes, and they're in Prep for a reason of their own: antioxidant defense.

• Shiitake extract showed antioxidant activity in a 2026 lab study, and it was gentle on human skin cells.⁵
• Turkey tail extract protected skin cells from free-radical damage in the lab.⁶

A 2024 review of 52 studies on mushroom extracts and skin cells found antioxidant and moisturizing activity across many species.⁷ Again, that's lab work, not human trials.

Are adaptogenic mushrooms a real thing in skincare?

Not really. "Adaptogen" describes something you ingest that helps your body cope with stress.⁸ Europe's medicines regulator has said the term isn't accepted in pharmacology.⁹ It has no defined meaning for something you put on your skin, so we don't use it.

What's true is simpler: sea fennel and these mushrooms come from organisms that cope with harsh environments, and they're rich in antioxidants. In Prep, that's part of the antioxidant pillar of our hormone-informed philosophy.

And snow mushroom?

Snow mushroom (Tremella fuciformis) is in Prep too, but for hydration, not texture. Its polysaccharide is a water-loving sugar chain that forms a light, hydrating film.¹⁰ In Prep it's layered with five molecular weights of hyaluronic acid and polyglutamic acid.

You may have read that snow mushroom "holds 500 times its weight in water." We looked for the source and couldn't find one in the research, so we don't say it.

 

With care,
Afsheen & Samantha