evidence: The nose swab can't damage the brain [...] The idea you could access the blood-brain barrier through a swab up the nose is a complete misunderstanding of what it is and how it works. [...] "The swab cannot reach the blood brain barrier without significant force that breaks several layers of tissue and bone. We have not seen any complications from Covid swabs in our neurology practice", says Dr Liz Coulthard, a committee member of the British Neuroscience Association (BNA).