Name: 隐藏在眼泪、耳垢和其他分泌物中的秘密（The Secrets Hidden in Your Tears, Earwax, and Other Secretions）
Uploaded: 2021-06-29T01:39:44.000Z
Duration: 8 min 48 s
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Very few people actually enjoy getting poked for a blood test.

In fact, it can be a reason some people avoid their physicians altogether.

And that is why scientists are thinking outside the needle

to create the next generation of diagnostic tests.

And it turns out, various secretions can tell us more about our bodies

than you might think, including sweat and tears… and also earwax.

When you think of analyzing bodily fluids,

blood might be the first one you think about,

but spit gives us about the same information and without needles!

In fact, saliva has similar components to blood,

because it is partly filtered blood plasma.

some of it is diverted from the blood into the salivary gland.

Then, the plasma mixes with water in the salivary glands,

which then gets into your mouth as saliva.

So, like blood, spit has antibodies and enzymes,

both of which are hugely valuable in making diagnoses.

Antibodies are made by the immune system when it detects viruses,

And enzymes are involved in basically every process in your body.

How much saliva someone produces, as well as the acidity of their spit,

can also be helpful for making diagnoses.

From a logistics standpoint, spit is pretty easy to collect compared to blood, as well,

and it's a cheap way to test larger populations without

any risk of spreading bloodborne pathogens.

scientists were originally concerned that it was too diluted to be useful.

But with advances in technology, tests are more sensitive and are able to

pick up on specific molecules at lower concentrations.

Like, saliva testing has been super helpful

during the COVID-19 pandemic in some communities.

So, scientists can potentially use saliva tests to test larger populations

for the presence of the virus or antibodies quickly and cheaply.

Similarly to spit, breath is also something you produce all the time.

When you exhale, you release carbon dioxide,

but your body also releases volatile organic compounds or VOCs,

a huge category of compounds that are able to stay suspended in the air.

These volatile compounds are usually generated

as byproducts of normal bodily processes.

But the VOCs in our breath also change as our health does.

For instance, our bodies make nitric oxide to combat inflammation.

So, one way to diagnose patients with chronic inflammation in the airways,

like from asthma, is to measure how much nitric oxide they're breathing out.

Scientists can also trace VOCs to other respiratory conditions

like cystic fibrosis and smoking-related conditions.

We have special devices for it that are similar to

the breathalyzers used to measure blood-alcohol content.

with gas chromatography or mass spectrometry,

two techniques that separate out different kinds of molecules.

Now, these techniques are used all the time in research,

But making, like, an “electrical nose” for medicine is still easier said than done.

It's taken almost 40 years, because collecting samples

and standardizing the methods has been challenging.

scientists have been able to smell out Parkinson's disease.

Right now, there's no definitive diagnostic test for this condition.

But in a 2018 study, scientists collected the breath

of patients with Parkinson's symptoms and observed a spike in benzaldehyde,

and acetophenone was observed in a slightly higher amount.

It's not clear what's special about these two compounds.

They're just a part of the spectrum of VOCs normally in our breath.

But if other researchers also notice this pattern,

these compounds could be a marker to help diagnose Parkinson's disease.

There's still a long way to go before electrical noses hit the market,

but these results are a step in the right direction.

Lots of breathing is sometimes accompanied by lots of sweating,

Although we couple sweating with working out or it being hot outside,

So someday, analyzing your sweat could provide doctors with real-time,

But for now, most of the studies have focused specifically on exercise.

Apart from a bunch of water, you can find electrolytes, metabolites,

and other small molecules like glucose in your sweat.

These molecules are circulating in your body all the time,

like, electrolytes move nutrients around your cells and also maintain your body's pH.

And because they're water-soluble, we lose some of them in our sweat.

Meanwhile, other small molecules reach the sweat

mainly by diffusion through the sweat glands.

And to keep track of them, some scientists are trying to use

A sensor like this could tell you all kinds of things about your body.

Like, the glucose in sweat can be correlated to how much glucose is in your blood.

And scientists have taken advantage of that

to determine if glucose is present in sweat during exercise.

Meanwhile, the levels of electrolytes and pH of sweat can

provide information on how hydrated someone is while exercising,

and let them know if they need a water break.

Lactate is generated when you do demanding exercises, like sprinting,

in cases where cells aren't all getting enough oxygen,

so some of them start functioning without it.