A person "smells blood"

General Questions
#1

I often hear the expression that someone “smells blood” and goes on the attack. I was wondering if this expression was a reference to sharks, specifically. Is it an old expression? Would it possibly predate whenever it is humans discovered sharks can smell blood.

It’s a curious expression since we normally cannot actually smell blood (apparently there are some medical conditions which does make a person’s blood smell certain ways)… And if we could smell blood we don’t have an instinct to attack the person bleeding.

I’m just curious where this expression came from and how old it is.

#2

As a combat OR nurse, I’m here to tell ya…you sure as hell can smell blood, and a nasty smell it is, too. That being said, you’re right, the expression comes from animals that are inspired to attack from smelling blood, though I’m not sure it specifically refers sharks. I think it’s meant to reference animals like bears, wolves, etc., that can tell if an animal is wounded and therefore weak.

#3

I agree. Sharks are not the only predator attracted to the scent of blood.

In addition to being a sign of wounded prey, blood can also signal that another predator has made a kill. Predators will check out the scene to see if it’s a weaker predator they can chase off and steal the kill from.

#4

I’ve heard we can smell a whole bunch of blood, but if I cut my finger i’m not going to smell anything. 6 pints of blood on the floor and yea i wouldn’t be surprised if there were some slight smell. I’ve heard it’s metallic. But mostly iv’e heard there are medical conditions that cause blood to smell a certain way. There’s that one case where it caused people to smell something funny and then pass out. I’ve never smelled blood. I even saw a bloody surgery once and the only thing i remember smelling is the smell of burnt flesh from the cauterizer - horrendous smell. The only smell that’s ever made me a little queasy in my entire life.

Also I realize sharks are not the only predator attracted to the scent of blood, but in my mind they’re the most stereotypical.

#5

Actually, I know from experience that a mere 1 pint of blood on the floor has a smell, and it also covers a surprisingly large area.

You’re right, a drop or two isn’t likely to have an odor anyone notices but blood does have a smell.

For that matter, the business end of butcher shops also smell of blood, but these days they seem to keep all that behind a door so the public doesn’t see/hear/smell that part of converting cows to steak and pigs to chops

#6

If I put my nose close to it, I can smell blood even from a small cut. Your nose is probably better than you think it is. Humans can distinguish more than 1 trillion odors.

The expression refers to predators in general being attracted and incited to attack by the scent of blood. Predators such as wolves and bears are far more sensitive to scent than humans are.

The idea that sharks “smell blood” probably much more recent. Actually, the expression that refers to sharks more specifically is sensing “blood in the water.”

#7

My guess is that it comes from when hunting (or being hunted!) was a common experience. Packs of dogs or wolves tracking prey get more assured/excited/focused when they have a blood spoor to follow as they know a kill will be more likely.