What Do Exosomes Actually Do? The Simple Science

By Dr Ivona Igerc, GDC-registered doctor and aesthetic practitioner, founder of Dr Ivy London. Last updated: August 2026.

Exosomes are microscopic, membrane-bound particles that cells release to send messages to other cells. Roughly one-thousandth the width of a human hair, they carry proteins, fats and genetic material as cargo. First identified travelling out of blood cells in 1983, they help coordinate processes throughout the body, from immune defence to wound repair.

That is the short answer. If you have heard "exosomes" mentioned in a skincare context and want to understand what the word actually means before you think about any product, this guide is for you. It stays with the biology: what exosomes are, what they are made of, what they carry, and what they do in the body. Skincare comes in only at the end, briefly and at the appearance level, because the science of exosomes in general and the marketing of any one serum are two different things.

What exactly is an exosome?

Think of almost every cell in your body as constantly sending out small, sealed packages to its neighbours. Exosomes are those packages. They are a type of extracellular vesicle, a general term for any particle a cell releases outside itself, and they sit at the smaller end of that family: roughly 40 to 160 nanometres across, averaging around 100, roughly one-thousandth the width of a human hair.

Nearly every kind of animal cell studied so far releases exosomes: blood, immune, nerve and skin cells among them. Plants release comparable particles, but with a nomenclature difference worth knowing. Plant vesicles can form by more than one route, and researchers describe the multivesicular-body pathway as the main one, though biogenesis research in plants remains relatively limited and isolated plant preparations are notably varied, spanning roughly 50 to 500 nanometres. Because a given preparation is therefore not a single uniform population, researchers use the cautious umbrella terms extracellular vesicles or, more precisely, plant-derived exosome-like nanovesicles (PENs) rather than exosomes proper (Liu et al., Journal of Nanobiotechnology, 2025). "Plant-derived exosomes" is common skincare-marketing shorthand, used the same way elsewhere here. Human exosomes have been identified in blood, saliva, breast milk and other body fluids, one reason researchers study them as a non-invasive window into tissues otherwise hard to reach.

What are exosomes made of?

An exosome has two parts worth understanding separately: the outer shell, and what it carries inside.

The membrane: a fatty outer shell

Every exosome is wrapped in a lipid bilayer, the same basic type of fatty membrane that surrounds a living cell, budded off during the exosome's formation. Studded across that membrane are surface proteins, including tetraspanins such as CD9, CD63 and CD81, commonly used by researchers as vesicle markers (Di Bella, Biology, 2022). Some membrane proteins may also participate in interactions with recipient cells, though how exosomes target and enter specific cells remains under study. This membrane is also what makes an exosome relatively sturdy: it can travel through blood and other fluids without immediately breaking apart.

The cargo: what do exosomes contain?

Inside that shell, exosomes carry a mixed cargo of proteins, lipids, and genetic material such as messenger RNA (mRNA) and microRNA, plus, in some cases, small fragments of DNA. A 2022 review in the journal Biology notes that the specialised EXOCARTA database has catalogued 9,769 proteins, 3,408 mRNAs, 2,838 microRNAs and 1,116 lipids identified across exosome studies to date (Di Bella, Biology, 2022). That figure illustrates the sheer diversity of molecules researchers have reported across exosome studies, not the contents of any single vesicle: it is an aggregate across many different studies, cell types and vesicle populations, and no individual exosome carries anything approaching the full catalogue. Not every exosome carries the same mix. The cargo reflects the cell that made it, so an exosome from an immune cell tends to carry different signals to one shed by a skin cell.

Where do exosomes come from? A short history

Exosomes were not discovered as an idea; they were discovered by accident, twice, within the same week. In 1983, two research groups working independently, one led by Rose Johnstone (published as Pan and Johnstone in the journal Cell), the other by Clifford Harding, John Heuser and Philip Stahl (published in the Journal of Cell Biology), were studying how immature red blood cells shed a surface protein called the transferrin receptor as they mature. Both groups saw the same thing under the microscope: the receptor was packaged into tiny internal sacs, then released from the cell in a burst of small vesicles.

Writing thirty years later about their own 1983 findings, Harding, Heuser and Stahl summarised the discovery plainly: "Exosomes are extracellular membrane vesicles whose biogenesis by exocytosis of multivesicular endosomes was discovered in 1983" (Harding, Heuser and Stahl, Journal of Cell Biology, 2013). The name itself came slightly later. As that same 2013 paper records, "the name 'exosome' for these extracellular vesicles was coined a few years later by Rose Johnstone."

Mechanically, "biogenesis by exocytosis" means this: a cell's outer membrane folds inward, creating an internal pocket called an endosome. Inside that endosome, the membrane folds inward again, budding off a cluster of small internal vesicles inside a larger structure called a multivesicular body (MVB). When the MVB reaches the cell's outer edge, it fuses with the outer membrane and releases its cargo of small vesicles to the outside. Those released vesicles are exosomes, sized roughly 40 to 160 nanometres in diameter, averaging around 100 (Kalluri and LeBleu, Science, 2020). It is an elegant piece of cell machinery: a cell builds its messages inside a shipping container, then ships the whole container out.

What do exosomes do in the body?

Once released, an exosome travels through the fluid around it, sometimes into the bloodstream, until it reaches another cell. It can dock onto that cell's surface and hand over a signal, or be taken inside the cell entirely, where its cargo is unpacked and put to use. Kalluri and LeBleu, writing in Science, describe exosomes as carrying "proteins, metabolites, and nucleic acids...into recipient cells" in a way that can "effectively alter their biological response."

That mechanism turns out to matter across a wide range of normal body processes:

• Immune signalling. Immune cells use exosomes to pass antigen information to each other, part of how the immune system coordinates a response.
• Tissue repair. Exosomes are being studied for roles in signalling associated with tissue repair; for example, exosomes released by mesenchymal stem cells have been investigated for a part in wound healing and tissue repair (Di Bella, Biology, 2022).
• Pregnancy. Exosomes are involved in the biological signalling between mother and developing placenta.
• Everyday tissue maintenance. Because almost every cell type sheds exosomes constantly, they are thought to be part of the routine background communication that keeps tissues coordinated.

Researchers also study exosomes because they can go wrong in disease. In cancer, tumour cells can use exosomes to influence nearby healthy cells or prepare distant tissue for the disease to spread, one reason exosome research has grown so quickly in oncology (Kalluri and LeBleu, Science, 2020). None of this is a skincare finding; it is the general biology that has made exosomes one of the most active areas in cell biology over the past decade.

What exosomes are, and what they are not

A lot of the confusion around this word comes from marketing shorthand. Here is the plain version.

Exosomes, in other words, are a biological category, not a legal one. Products containing them are regulated differently depending on how they are sold and used; readers who want that detail can see the MHRA's guidance on borderline products.

Why skincare formulators became interested in exosomes

Skin cells communicate with each other the same way other cells do, using signals that include exosomes. That basic observation, part of normal cell biology rather than anything specific to one brand, is what drew cosmetic formulators to the idea of exosome skincare in the first place, and it is where this article has to be precise. The biology above is what prompted the research interest; it is not evidence about what a finished topical product does. General cell-biology research does not show that exosomes or exosome-like vesicles applied to the skin's surface cross the skin barrier, reproduce the body's own cell-to-cell signalling once there, or deliver any particular benefit in a finished cosmetic formulation. Those are separate, narrower questions, answered by evidence on the specific formulation, not borrowed from the biology of how cells communicate.

That is deliberately as far as this article goes into the skincare question, because it is not this article's job to answer it in depth. Dr Ivy London's Regenerative Exosome Serum is formulated with plant-derived exosomes from Centella Asiatica and is positioned as a daily cosmetic step to support the appearance of firmer, smoother-looking skin as part of a routine. The research above, on exosomes generally, is not evidence about how any single finished serum performs.

For the fuller picture of how exosome skincare is actually used, what results are realistic, and how it compares with other actives, read our doctor's guide, What Is Exosome Skincare? A Doctor's Guide. For a closer look at what the published evidence does and does not support for topical serums specifically, see Do Exosome Serums Actually Work? What the Evidence Says. Questions about safety and UK regulation, and about how plant, human and stem-cell sources differ, are covered in forthcoming guides rather than repeated here. You can also read more on our About Exosomes and Science pages, and about the practitioner behind the brand on the About Dr Ivy page.

Frequently asked questions

What are exosomes in simple terms? Exosomes are tiny, naturally occurring particles that cells release to send biological signals to other cells, a bit like sealed messages passed between neighbours. They are far smaller than a cell, roughly 40 to 160 nanometres wide, averaging around 100, and every major cell type is thought to produce them, not only skin cells.

What are exosomes made of? Each exosome has an outer shell made of a lipid bilayer, the same fatty membrane material that surrounds a living cell, studded with surface proteins including tetraspanins such as CD9, CD63 and CD81. Inside that shell sits the cargo: proteins, fats and genetic material such as RNA, and sometimes small fragments of DNA.

What do exosomes contain? Exosomes carry a mixed cargo of proteins, lipids, messenger RNA, microRNA and, in some cases, DNA fragments. The exact mix varies by the cell that released it, which is why exosomes from different cell types carry different biological information.

What are exosomes used for? In the body, exosomes are used for everyday cell-to-cell communication, including roles in immune signalling, tissue repair and pregnancy. In research and medicine, they are being studied as disease markers found in blood and other fluids, and as potential delivery vehicles for future therapies. In skincare, they are used as an ingredient in some serums and creams, applied topically, at the appearance level rather than as a medical treatment.

What does the word "exosome" mean? "Exosome" describes a vesicle released, or exported, from a cell, to the outside. The name was coined by the researcher Rose Johnstone a few years after she and her colleagues first identified the particles in 1983, published in the same week as an independent discovery by Clifford Harding, John Heuser and Philip Stahl.

How big is an exosome? Most exosomes measure roughly 40 to 160 nanometres across, averaging around 100 nanometres. For context, that is far too small to see with a standard light microscope; visualising them requires electron microscopy or specialised particle-tracking equipment.

Who discovered exosomes, and when? Exosomes were first described in 1983 by two independent research groups within the same week: Rose Johnstone's team, publishing in the journal Cell, and Clifford Harding, John Heuser and Philip Stahl, publishing in the Journal of Cell Biology. Both groups were studying how a protein is shed from maturing red blood cells when they observed the vesicle-release mechanism now known as exosome biogenesis.

The takeaway

Exosomes are not a skincare invention. They are a normal, well-documented part of how cells throughout the body communicate, first identified more than four decades ago and now one of the most active fields in cell biology, from immunology to cancer research. Understanding that background is what makes it possible to judge any exosome skincare claim honestly: the biology is real and well established; what any single topical product can achieve with it is a separate, much narrower question, covered in full in our doctor's guide to exosome skincare.

Sources cited in this article

1. Di Bella, M.A. "Overview and Update on Extracellular Vesicles: Considerations on Exosomes and Their Application in Modern Medicine." Biology, 11(6):804, 24 May 2022. https://doi.org/10.3390/biology11060804
2. Harding, C.V., Heuser, J.E., Stahl, P.D. "Exosomes: Looking Back Three Decades and Into the Future." Journal of Cell Biology, 200(4):367-371, 18 February 2013. https://doi.org/10.1083/jcb.201212113
3. Kalluri, R., LeBleu, V.S. "The Biology, Function, and Biomedical Applications of Exosomes." Science, 367(6478):eaau6977, 7 February 2020. https://doi.org/10.1126/science.aau6977
4. Liu, H. et al. "Plant-Derived Exosome-Like Nanovesicles: A Novel Therapeutic Perspective for Skin Diseases." Journal of Nanobiotechnology, 23:640, 10 October 2025. https://doi.org/10.1186/s12951-025-03715-1

All four fetched and verified directly on PubMed Central on 1 August 2026.