Many thanks folks. The pax in question lives in the Johannesburg area. I asked my sister to check with her friend and some of the feedback was:
Not sure of the very first occurence, it could have been in 2018 when we went to Australia with Emirates or it could have been on BA to Boston. That time the air was very low and 2 people actually fainted and were given oxygen. I did not actually faint but the blood drained from my face leaving me white and feeling faint. I could not have stood up. I also start vomiting. I was given oxygen and felt better within half an hour or less. I probably had a [brand name of a paracetemol and codeine, over the counter tablet] and a glass or two of wine with dinner (my doctor has since told me that [name] is not a good drug to take.) The cabin crew admitted that the air had been turned down very low. They turned it up and no more passengers had fainting problems. I thought no more about it.About a year ago I was diagnose with Type 2 diabetes and I did wonder if this was a contributing factor. The second time was on 19th April 2022 when we flew Quatar airways QR1364 to Doha and then on to Dallas QR 731. I think it must have been the first leg. Each incident has been at night and after a glass of wine and probably a [tablet] as, by the time I get onto the plane I have a splitting headache. Again I was given oxygen and the air was turned up and the faintness and vomiting have passed quite quickly.
We flew back to JHB from Boston (AA 108 ) on the night of 7th July 2022 and the faintness and vomiting happened again and I was given oxygen and the stewardess said they were turning up the air but this time I did not feel that the air in the cabin was low. This time I was still feeling slightly squeamish when we landed in London. I did not have an incident on the flight from London to Jhb. but I sat very still and had no wine. All flights were at night.
On arriving home my doctor had no explanation for the problem and declared me fit and healthy. I hope this all makes some sort of sense and again thank you for your interest.
The CC did take the pax name and details and took that to the FD, hopefully to be put in the log?
The pax does not detail what they mean the 'air was low' for, as we know it is only the temperature than can be altered.