Fact check: No, the COVID-19 nasal test doesn't swab the blood-brain barrier

The claim: The spot that gets sampled during the COVID-19 test is the blood-brain barrier  

A July 6 post claims that the area sampled during a COVID-19 nasal swab is a part of the body called the blood-brain barrier. An image accompanying the post associates the blood-brain barrier with the target site for sample collection. 

"I was wondering why the PCR test for COVID-19 had to be so far back and it got me thinking... how far does it go?

"So I did some research and found these two pictures and overlapped them. The surprising evidence was shocking!

"The blood brain barrier is exactly where the swab test has to be placed.

"Coincidence??? I don't think so."

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The author of the post intensifies the claim by stating if the blood-brain barrier is compromised by a contaminated test, a condition called "leaky blood-brain barrier," or inflamed brain, results leading to bacterial infection, toxin exposure, a whole host of syndromes and diseases, and ultimately death. 

However, the author later concedes it's not necessary for the blood-brain barrier to be directly jeopardized.

"(I)t doesn't need to penetrate the blood brain barrier. It only needs to violate and bypass the mucus membrane, the olfactory epithelium, then toxins can access the olfactory nerves and reach the neurons/brain," he writes.

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"This might be a way for the evil agenda folks to bypass this protective layer... and actually increase the risk of sickness," he claims. 

The author of the post has not yet responded to USA TODAY's request for comment.

What is the blood-brain barrier? 

Blood vessels are channels through which blood – the fluid providing the human body with vital nutrition, oxygen and waste removal – circulates. Some blood vessels surround the central nervous system, forming a specialized layer called the blood-brain barrier. It tightly regulates the movement of molecules, ions and cells between the blood and the central nervous system. It's very restrictive nature has proved problematic for therapeutic drug delivery and many scientific efforts are investigating methods to bypass this vascular firewall. 

So is the blood-brain barrier sampled during a COVID-19 nasal swab? Quite the contrary: It's not even within anatomical reach.

"There are three layers of protection in the nose. There's the mucosal lining which covers the inside of the nose. There's the olfactory epithelium (involved in sense of smell). The inside, the dura mater, which means 'tough mother,' is a tough lining of skin around the brain. It's hard to penetrate through (it) without something sharp," said Dr. Shawn Nasseri, an ear, nose and throat surgeon in Los Angeles, in an interview with USA TODAY. 

Don't worry - a COVID-19 test isn't going to hit your brain, or even close.

Nasseri, who has performed COVID-19 nasal swabbing countless of times in his own clinic, emphasized that piercing the dura mater to get to the blood-brain barrier with the typical soft swab used, even with poor sampling technique, was "very incredibly unlikely."

Dr. Yvonne Maldonado, a professor of pediatric infectious disease at Stanford University School of Medicine who recently authored a study investigating COVID-19 self-swabbing tests, agreed. 

"As far as we are aware, there is no scientific basis for the idea that nasal swabs can enter or damage the blood brain barrier," she wrote in an email to USA TODAY.      

Nasal swabbing and the olfactory epithelium

During a COVID-19 nasal test, Nasseri said normally the nasopharynx, an air-filled cavity at the top of the respiratory tract 3 inches behind the nose, is swabbed. The swab is in the nasopharynx for only a few seconds but can be very uncomfortable for patients.  

"It's a little bit of a trauma for a lot of people, they feel it's very invasive," he said.

And while some patients can have significant reactions, specifically fainting or light-headedness likely due to the "seal dive" reflex, illness due to olfactory epithelium injury during sampling is doubtful.

"Let's say you took a knife and scraped the epithelium, long before that bacteria (or other harmful agents) hit the blood supply, you would know," Nasseri said. The usual telltale sign would be meningitis, inflammation of the tissues surrounding the brain and spinal cord, whose cardinal symptoms of fever, headache and stiff neck are hard to miss. 

It's important to note that the olfactory epithelium is ordinarily damaged by daily allergens, airborne pollutants, microorganisms and other potentially harmful substances. Thankfully, stem cells within the structure are there to regenerate it every few weeks or so.      

Nasal swabbing is also not unique to COVID-19 testing. Nasal swabs, or nasopharyngeal cultures, have been mentioned since the early 20th century and are routinely used to diagnose respiratory infections, whether caused by bacteria, fungi, or viruses. Nasal swabs are considered generally safe for most individuals.          

Our ruling: False

We rate the claim that the COVID-19 nasal test samples the blood-brain barrier as FALSE because it is not supported by our research. The blood-brain barrier, a system of vessels surrounding the central nervous system, is not readily in reach without piercing through several protective layers – an unlikely feat with a soft nasal swab. The additional claim that swabbing leads to damage in the olfactory epithelium is also unlikely.  

Our fact-check sources: 

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