Stem cell skincare: what growth factor and secretome labels really mean

"Stem cell" has been a selling phrase in skincare since the late 2000s, and the label vocabulary keeps growing: growth factors, conditioned media, secretome, exosomes. The words sound like they come from a cell therapy lab, and some of the ingredients really do. What they do on the surface of your face is a different question, and the answers depend heavily on which of several quite different things a product actually contains.

This page sorts out the terms, explains how US rules treat these products and compares the published evidence with the few measures that have strong evidence against skin aging. It names no brands and recommends no products.

Three very different things sold under one phrase

Plant "stem cell" extracts

Plants keep pockets of undivided cells (meristems) that can grow new tissue, and a cut plant surface can form a lump of undifferentiated cells called callus. Ingredient makers grow such plant cells in bioreactors, break them open and sell the extract. The ingredient list may show names like "Malus Domestica Fruit Cell Culture Extract".

Nothing in these extracts is alive by the time it reaches a jar, and plant cells could not turn into human cells in any case. Plant growth regulators are chemically unrelated to human growth factors and do not act on human skin receptors in the same way. What the extracts can contain are ordinary plant compounds such as polyphenols, which may work as antioxidants or moisturizers like many other botanical ingredients.

Human cell conditioned media and "secretome"

When human cells grow in a lab dish, they release proteins and other molecules into the surrounding liquid. That spent liquid, filtered of cells, is called conditioned medium. Everything the cells release is sometimes called their secretome. Cosmetic suppliers make conditioned media from human skin fibroblasts and from stromal cells taken from fat or umbilical cord tissue (the same family of cells described on our page about mesenchymal stromal cells). Labels use words like "conditioned media", "secretome", "lysate" or "cell culture extract".

These products do contain human signaling molecules. How much, how stable they are in a cream and whether they get past the skin barrier are the open questions. The culture methods behind them are similar to those on our stem cell technology page, minus the release testing a therapy would need.

The European Union treats this category very differently from the US: its cosmetics regulation lists "cells, tissues or products of human origin" among substances banned in cosmetic products.

Exosomes

Exosomes are tiny membrane bubbles, roughly 30 to 150 nanometers across, that cells release and that carry proteins and genetic material between cells. Researchers study them as possible therapies and drug carriers. In skincare and at med spas, "exosome" products are usually made from human stromal cells, plant cells or, in some cases, animal sources.

Growth factors: large molecules, a tight barrier

Growth factors are signaling proteins that tell cells to divide, move or make collagen. In wound healing they matter a great deal. Epidermal growth factor (EGF) is the one most often named on labels, usually in its recombinant form made by bacteria, yeast or plants. On an ingredient list, recombinant human EGF often appears as "sh-Oligopeptide-1", where "sh" stands for synthetic human.

The catch is size. The outer layer of skin, the stratum corneum, keeps most large molecules out. A widely cited rule of thumb from dermatologists Jan Bos and Marcus Meinardi (2000) holds that compounds much heavier than about 500 daltons penetrate intact skin poorly. EGF weighs around 6,000 daltons, and most other growth factors are larger. Some may get in through hair follicles or damaged skin, and formulas try various carriers, but the intact barrier is a real obstacle that marketing copy rarely mentions.

Researchers have also raised a theoretical concern: growth factor signaling is involved in some cancers. There is no evidence that topical cosmetic use causes cancer, but long-term safety data are thin, which is part of why claims about "regenerating" skin deserve care.

Exosomes and the FDA

On December 6, 2019, the FDA issued a public safety notification on exosome products. It stated that there were no FDA-approved exosome products, that exosomes intended to treat or prevent disease are regulated as drugs and biological products requiring approval, and that patients in Nebraska had suffered serious adverse events after receiving unapproved exosome products. The agency has since sent warning letters to several companies marketing exosome products for medical uses.

That notification was about treatments, not lipsticks. But the line between a cosmetic and a drug depends on what is claimed and how a product is used, which brings us to the rules.

Cosmetic or drug? How US rules sort it

US law sorts products by intended use, which the FDA reads from labels, advertising and context. A cosmetic is meant to cleanse, beautify or change appearance. A drug is meant to treat or prevent disease or to affect the structure or function of the body. The FDA's guidance page Is It a Cosmetic, a Drug, or Both? gives examples, and claims that a product will "regenerate cells" are among them: that kind of claim makes a product a drug in the agency's eyes.

The practical gap is large. Cosmetics and their ingredients, except color additives, do not need FDA approval before sale. Drugs generally need to show safety and effectiveness first.

The Modernization of Cosmetics Regulation Act, signed into law on December 29, 2022, was the largest change to US cosmetics law since 1938. Companies now have to register facilities and list products with the FDA, report serious adverse events and keep records showing that each product's safety is adequately substantiated. The FDA gained the power to order recalls. What MoCRA did not create is premarket review of whether a cosmetic works.

That explains the careful wording on many jars: "improves the appearance of fine lines" is a cosmetic claim, while "stimulates collagen production" or "repairs damaged cells" reaches into drug territory.

What the published studies look like

Studies of stem cell and growth factor cosmetics do exist, and some are decently run. The typical one, though, shares several features:

• A few dozen participants, sometimes fewer.
• Eight to twelve weeks of use, too short to say much about aging.
• Funding or authorship from the ingredient supplier or brand.
• No comparison with the same base cream minus the active ingredient, or comparison only with the untreated other half of the face.
• Outcomes measured by investigator photo grading, device readings of moisture or elasticity, or participant questionnaires.

These designs can show that people liked a cream and that their skin was better hydrated. They are weak at showing that a specific ingredient changed collagen or reversed photoaging, and almost none are large enough to pick up uncommon side effects.

What does have strong evidence

For comparison, a short list of measures with large or long trials behind them. Our science desk covers them in more depth in skin aging: what the evidence supports.

• Daily sunscreen. A randomized trial in Nambour, Australia, published in the Annals of Internal Medicine in 2013, followed 903 adults under 55 for about four and a half years. The group assigned to daily sunscreen showed no detectable increase in skin aging over the study, unlike the group using sunscreen at their own discretion.
• Retinoids. Prescription tretinoin has been approved by the FDA for fine wrinkling in sun-damaged skin since the mid-1990s and has many controlled trials behind it. Over-the-counter retinol is weaker and has a smaller evidence base.
• Not smoking. Smoking is consistently linked with earlier and deeper wrinkling in population and twin studies.

None of these is new or exciting, which is partly why they are rarely marketed with the same energy.

Reading the label: a checklist

1. Find the actual ingredient. Is it a plant cell culture extract, a human cell conditioned medium, a recombinant growth factor (such as sh-Oligopeptide-1) or something labeled exosome? Each is a different thing.
2. Note its position. Ingredients are listed in descending order down to 1 percent; an active near the end may be present in very small amounts.
3. Read the verbs. "Appearance of", "looks" and "feels" are cosmetic claims. "Regenerates", "repairs cells" or "heals" are drug claims the FDA has not reviewed for a cosmetic.
4. Look for living cells. No cosmetic contains living stem cells that act on your skin. A label implying it does is overstating.
5. Check the evidence offered. "Clinically tested" means some test was run, not that the FDA reviewed it. Ask how many people, for how long, compared with what, and who paid.
6. Separate cosmetics from procedures. Products applied after microneedling or injected at a clinic are no longer simply cosmetics, and the FDA's 2019 notification applies to exosome treatments.

Questions readers ask

Can a cream deliver live stem cells to my skin?

No. Cells do not survive in a cream, and even living cells applied to intact skin could not settle in and become part of it. "Stem cell" on a cosmetic label refers to what an ingredient was made from, not to living cells in the product.

Are human-derived ingredients safe?

Suppliers screen donors and test for contamination, and under MoCRA the company selling the product must keep records supporting its safety. There is no FDA premarket review of that evidence, and long-term data are limited. The EU's ban reflects a more cautious reading of the same uncertainty.

Are exosome facials an approved treatment?

When this page was updated, the FDA had not approved any exosome product for any use. Exosome treatments marketed to treat a condition fall under drug and biologic rules, which is the subject of the agency's 2019 notification.

Is a growth factor serum the same as a cell therapy?

No. A cell therapy is a regulated medical product with manufacturing controls, release testing and clinical trials. A serum may share a starting material, but nothing about its sale requires evidence that it works.

Do plant stem cell extracts do anything?

They may add antioxidant or moisturizing compounds, as many plant extracts do. Published studies are small, and none show that plant cells activate human skin stem cells. A product's sun protection factor, listed as a drug fact on US sunscreens, carries far more evidence than its plant extract.