Why does your saliva start to taste like blood if you ride your bike up a hill or run fast for a while?
Edit: Thanks for the Awards and the nice Comments.
Also blew up bigger than I thought!
In: Biology
Some people have provided correct and detailed explanations that I think might be a bit too high-level for ELI5, so I’ll see what I can do.
First, it isn’t your saliva that tastes like blood, it’s the air coming out of your lungs. You should notice that the taste gets stronger if you exhale forcefully.
Second, this is basically caused by your heart/lungs working way harder than they’re used to, which results in some blood getting forced into your lungs. The blood contains a lot of iron, which is responsible for that metallic taste that you instantly recognize as blood.
Am I the only person this has never happened to?
I have exercise induced asthma and I get this sensation right before I get an asthma attack after cardio exercise. It’s such a strong blood taste I used to think I was going to spit out blood but when I spit it was always just saliva. So learning the science now helps it all make sense.
Since there are 397 comments here, I assume no one will ever see this.
The top answer is wrong. It has to do with the decreased blood pH from retained CO2.
The effect is a known symptom of patients with metabolic acidosis for instance. It is also a warning sign when free-diving. Obviously there is nothing moving into your mouth when you are underwater.
You can taste it yourself if you hold your breath for 90 seconds.
I have low potassium and magnesium and it tastes like penny’s, I get muscle weakness, it feels like my legs are cooked noodles, and they get very heavy.
Talk to your doctor about a blood test. But its probably something else.
There are many theories but no one knows why, some of the explanations here are a likely culprit but overall there likely isn’t a single root cause for everyone.
Not everyone experiences it, and it seems not to be directly correlated to your level of fitness either.
Also not everyone experiences it due to stress levels alone for example I only experience it when running in cold weather, the likely explanation for me is that colder dryer weather might cause more raptures in blood vessels in the throat, nose and tear ducts which means more blood cells get funneled into my mouth as I exhale or through the mucus.
P.S. some people mentioned metallic taste before throwing up, the metallic taste before throwing up isn’t related to this, that happens every time you are about to throw up and it’s due to a reflex trigger that increases saliva production to provide lubrication to reduce choking and to protect your throat and mouth from your gastric acid and any thing you might have swallowed that didn’t or couldn’t be digested (historically and even today some animals including mammals throw up bones that they swallow and also may throw up other particulates like sand or small rocks that they swallow intentionally or unintentionally during feeding, so the vomit reflex is likely shared across all of mammals just like the mammalian diving reflex).
You could quite likely cause that sensation at will by thinking about throwing up.
**Eli5 version**: Our blood contains iron. When you do strenuous exercise the pipes supplying blood to the balloons in your chest start leaking some of that iron-containing part of blood. When the balloons deflate, that’s when you exhale, some of that iron reaches your mouth from those balloons and your taste-thingamagigs tell you that you have iron in your mouth.
Oh god I figured it was just because I’m a weakling. The two people I’ve ever mentioned it to said it never happened to them.
This is weird. I work out all the time and yace never noticed any change to the taste of saliva. Interesting, though.
I’ve never had that happen that I know of, but I will say that I have really bad teeth and have definitely spent some time tasting blood. Ok cool. Bye.
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