Mass hysteria in the form of mass faintings also occurs regularly in factories and schools in Cambodia. It is believed that the cause of these events is primarily psychological, but physical conditions, such as over-heating or lack of fresh air, malnutrition, stress and overwork, also play a part in creating a favorable environment for mass fainting episodes to occur.

The mystery of screaming schoolgirls in Malaysia
By Heather Chen BBC News, Kelantan, Malaysia
11 August 2019
It was a quiet Friday morning last July when pandemonium broke out at a school in north-east Malaysia. Siti Nurannisaa, a 17-year-old student, was at the centre of the chaos.
This is her account of what happened...

Mass hysteria, or mass psychogenic illness, as it's also known, is the rapid spread of physical symptoms such as hyperventilation and twitching among a substantial group of people - with no plausible organic cause.

"It is a collective stress response prompting an overstimulation of the nervous system," says American medical sociologist and author Robert Bartholomew. "Think of it as a software problem."

The mechanisms behind mass hysteria are often poorly understood and it is not listed in the DSM - the manual of mental disorders. But psychiatrists like Dr Simon Wessely from King's College Hospital in London view it as a "collective behaviour".

"The symptoms experienced are real - fainting, palpitations, headaches, nausea, shaking and even fits," he says. "It is often attributed to a medical condition but for which no conventional biomedical explanation can be found."

Transmission, he adds, "is largely due to psychological and social factors".
https://www.bbc.com/news/world-asia-48850490

I thought it was the red baseball caps that made people go hysterical but apparently, there is more to it.

The lynch mob. Pack mentality. Very frightening. ^^ The prelude to Kristallnacht.
One of my reoccurring nightmares is the communal violence at the time of Partition in India, described in the classic Freedom at Midnight. I had always imagined i could avoid a mob going feral until i read this book - then i realised what an all encompassing typhoon it could be.
I have recognised it, on a smaller scale, many times since. It is one of the reasons i don't like "street justice", it's just like a pack of dogs when they pick on a vulnerable individual - but fuelled by righteousness.

On a less hysterical note, i suspect it is some of the chemicals they use, that are partly responsible for the mass faintings in garment and shoe factories. Glues, fire retardants, "starching" compounds - combined with the heat, exhaustion, nutrition etc.