Social media users are sharing posts which claim that nasal swabs being used to test for COVID-19 draw samples from the blood-brain barrier, which if compromised can lead to brain inflammation and death. This claim is false. It is not anatomically possible for tests to reach the blood-brain barrier, according to Public Health England. Instead, the nasal swabs being used in the Polymerase Chain Reaction (PCR) test, the preferred testing method in England, collect samples from the upper respiratory tract.

The posts have been shared over 1,000 times on social media. Examples can be seen here , here , here , here and here .

Most examples of the post show images of a nose swab overlapped with a picture of a brain, with embedded text above which reads“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? [...] The blood brain barrier is exactly where the swab test has to be placed. Coincidence??? I dont [sic] think so.”

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The image is accompanied by text in many Facebook posts: “If, in some way, your Blood-Brain Barrier is compromised, it becomes a 'Leaky Blood-Brain Barrier' which is an inflamed brain! It then allows bacteria & other toxins to enter your brain & infect the brain tissue which can lead to inflammation and sometimes death.”

The blood-brain barrier does filter out drugs and other substances in the blood so they cannot reach the brain. It is correct that if the blood-brain barrier is broken, the brain may be exposed to toxins, which may be an important factor in long-term brain changes ( here ).

However, a spokesperson for Public Health England told Reuters the claim that COVID-19 tests need to collect samples from the blood-brain barrier is not true. PHE said that this was not anatomically possible: “There is no point in the respiratory tract or nasal cavity where the brain is accessible. It would not be possible to touch the brain with a swab without drilling through the cribriform plate.”

The cribriform plate forms the roof of the nasal cavity ( here ) .

UK Government advice updated on July 7 says that samples for COVID-19 tests should be taken from the upper respiratory tract ( here ).

A previous false claim regarding the PCR test was debunked by Reuters Fact Check here .

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VERDICT

False. It is not anatomically possible for COVID-19 tests to collect samples from the blood-brain barrier; instead they target the upper respiratory tract.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here .