Guardian (8/9/25) Mass psychogenic illness’ plausible cause of toxic substance alert at Heathrow, says scientist
Guardian (9/9/25) Man arrested on suspicion of bringing teargas to Heathrow airport
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"One Day Later"
Guardian (9/9/25) Man arrested on suspicion of bringing teargas to Heathrow airport
Police were called to Heathrow late on Monday afternoon when 21 people fell ill in Terminal 4. Initial reports suggested a hazardous material could be involved and part of the airport was evacuated. But when the emergency services conducted a thorough search, no trace of any adverse substance was found.
A source within the Metropolitan police subsequently suggested the event could be something quite different – a case of mass hysteria. And some experts agree.
“What happened at Heathrow is almost certainly an episode of mass psychogenic illness that is anxiety-based,” said Dr Robert Bartholomew, a University of Auckland sociologist who is an expert on the subject.
He said anxiety-based cases were typically triggered by the sudden perception of a toxic agent – such as an unfamiliar smell. “Common symptoms include headache, overbreathing, dizziness and fainting,” he said, noting episodes tended to come out of the blue with victims often recovering within minutes.
Bartholomew stressed the illness was not a mental disorder and victims were not psychologically disturbed.
Prof Sir Simon Wessely of King’s College London, who was part of the team, said it was “a bit early” to come to judgments about the Heathrow event and it was unclear whether there was an unusual odour or what investigations were done to eliminate other causes. But he added: “If all these come to nothing, then yes, this may be an episode of what we now call mass sociogenic illness.”
Wessely said there was nothing unusual about the events at terminal 4 on Monday: “It happens all over the world every day, particularly in crowded spaces like schools, concerts, crowds, factory floors etc. The only reason this made the news was because of the fact it was at Heathrow and led to major flight disruptions.”
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"One Day Later"
Police have arrested a man on suspicion of bringing teargas into Heathrow airport, which caused Terminal 4’s check-in area to briefly shut down.
The check-in area at the UK’s main international airport was evacuated for around three hours on Monday evening as emergency services probed a “potential hazardous materials incident”.
A Metropolitan police spokesperson said a 57-year-old man had been arrested after urgent inquiries on suspicion of possession of a firearm (CS spray) and “causing a public nuisance”.
After searching the area, Met officers located a canister of “what is believed to be CS spray”, which was “thought to have caused a reaction to those within the airport,” the police said.
CS spray is a riot control agent, also known as teargas, which can cause a burning sensation to the eyes, throat, lungs and skin.
A source in the Met Police initially suspected that the incident could have been a case of “mass hysteria” before the canister was located, after officers scoured the area and were unable to find the source of the hazardous substance passengers had reported.
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