Clinics use these words interchangeably. They are not interchangeable, and the difference determines what a treatment can plausibly achieve.
The two families that matter to patients
Haematopoietic stem cells (HSCs) rebuild blood and immune systems. They are found in bone marrow, circulating blood, and umbilical cord blood. This is the family behind FDA-approved transplant medicine.
Mesenchymal stromal cells (MSCs) are what nearly every "stem cell clinic" is actually selling. They come from bone marrow, fat, or umbilical cord tissue. The original hope was that they would become new cartilage or new nerve tissue. Current understanding is that they mostly act by releasing signalling molecules that influence inflammation — which is why many researchers now avoid calling them stem cells at all.
If a clinic offers you an injection for your knee, your back, or an IV drip for a chronic condition, you are almost certainly being offered MSCs.
Your cells or someone else’s
Autologous means the cells come from your own body. No rejection risk, but the harvest is invasive, and cell quality declines with age and illness — meaning the patients most likely to seek treatment often have the least useful cells.
Allogeneic means donated cells, usually from umbilical cord tissue after a healthy birth. No harvest procedure, more consistent cell quality, but greater regulatory scrutiny in the US.
Exosomes are not stem cells
Exosomes are tiny vesicles released by cells. They contain signalling molecules but are not living cells and cannot multiply or become tissue. They are marketed as a cheaper, simpler option. No exosome product has FDA approval, and the FDA has issued warnings about them. The evidence base is thinner than for MSCs.