Back in September 2016, I was flying back from Los Angeles to Vilnius via Frankfurt. I was with my friend and we had an 8 hour layover in Frankfurt. We were so tired after the 12 hour flight from LA, that we only left the plane, found a place to crash at the airport and went to sleep. After a few hours I woke up to find my friend looking slightly scared. When I asked what had happened, she told me that she just had an anaphylactic shock, after eating a tortilla from a shop, which was with a sauce, which contained probably like 0.000001% nuts. Her throat started swelling and she had difficulties breathing. She managed to take a few pills she had with her, which help with the swelling a bit. She was scared and the pills made her less conscious and sleepy. As I said, I found out about the whole accident after I woke up, she didn't care to wake me up before. We rushed through the whole airport to find a medical point, which was landside. She got more, stronger pills, after which she was even less conscious. Eventually we boarded our plane for the final leg and my friend immediately after taking her seat fell asleep and remained asleep for the take off. About half into the flight (it was already totally dark outside) she woke up, looked out the window and asked why we were still on the ground, so for the next couple of minutes I was trying to convince her that we were already in the air.
It was a really scary experience for me, as I was constantly thinking that the shock might come back in her sleep and she might stop breathing.
FUN FACT: after that accident, I started to be scared of flying. For the next year or so I wasn't even aware that it might have been caused by that accident, but some guy told me how hard or scary experience, even not directly related to the fear, in the end it wasn't a plane accident, might cause different traumas and fears.
FUN FACT 2: I study aviation and fly around 10 times a year.