blood poisoning
Meaning of blood poisoning: An everyday phrase covering two different medical problems, which is why careful writing has retired it in favor of precise terms.
Definition of blood poisoning
Blood poisoning is a lay term for a serious infection that has reached the bloodstream and is making the whole body ill. Medicine has replaced it with two more precise words: bacteremia, meaning bacteria are present in the blood, and sepsis, meaning the body's reaction to an infection has begun damaging its own organs. The old phrase blurs the two together.
Why did the older terms fall out of use?
They described a mechanism that turned out to be the wrong one. Septicemia and blood poisoning both implied that harm comes from organisms and their poisons circulating in the blood. What actually causes the collapse in most cases is the body's own response: a flood of signalling molecules that widens vessels, leaks fluid out of them, triggers clotting inside small vessels and starves organs of oxygen. Blood cultures grow nothing at all in a large share of people who are severely ill with sepsis, which the older wording cannot explain.
How do the terms differ?
| Term | What it means | Standing |
|---|---|---|
| Bacteremia | Bacteria detectable in the blood | Current; may cause no illness at all |
| Sepsis | Organ damage from the response to infection | Current, and the term that matters |
| Septicemia | Organisms and toxins circulating | Outdated and imprecise |
| Blood poisoning | Any of the above, loosely | Lay usage only |
The pairing that surprises people is that bacteremia can be harmless, since even brushing teeth pushes bacteria briefly into the blood, while sepsis can kill with no organism ever recovered from a blood sample. Fungi and viruses can drive it too.
What else gets called blood poisoning?
The red line tracking up an arm from an infected cut, which many people read as poison spreading through the blood. It is lymphangitis, inflammation of a lymph channel draining the wound, and it runs in the lymphatic system rather than in a vein. It is a warning that infection is spreading, but it is not organisms in the bloodstream. The word toxemia is sometimes offered as a synonym as well, which it is not, its main surviving use being an old name for a pregnancy complication involving raised blood pressure.
Also known as
Used in a sentence
The referral letter used the phrase blood poisoning to describe the collapse.
Good to know
Sepsis is defined by organ dysfunction arising from the response to an infection rather than by organisms in the blood, so blood cultures are frequently negative in severely ill people, and toxemia is not a synonym for either term.