DH and I are away in the camper van. Just after midnight last night I needed the loo - the van bathroom is rather claustrophobic and has no air vent, so when I suddenly felt hot I just hurried to finish and get out.
But the heat suddenly washed over me in a wave and I started to sweat profusely. I recognised the feeling that I was going to faint and made it out to one of the seats, but my vision was fuzzy and all my limbs were weak. I was desperate for fresh air but didn't have the strength to open the door, so I was slumped in a chair groaning and trying to take deep breaths when DH woke up.
He opened the door for me and I was leaning out gasping for cold air (and yawning), but still couldn't move. He persuaded me to go back towards the bed so I could lay down, and that bit is hazy - he says I fell heavily just in front of the bed, and I certainly have a bruise on my head and knee. 
He bodily lifted me and got me onto the bed.
As soon as I lay down it took less than 2 minutes to feel 100% better. DH thinks I had a panic attack, but I know that was a faint. I don't really understand why...but within 30 minutes I was having the most awful diarrhoea (sorry if TMI), about 5 episodes in 2 hours. It eventually stopped and I drifted off to sleep at 3am.
The thing is, other than the fainting and the subsequent shits, at no time did I feel especially "unwell" or ill - I don't have any other symptoms of a stomach bug or food poisoning or anything, I'm fine today (just tired).
So did I faint because my system was preparing for a purge - or was the runs an after effect of fainting? Google suggests the latter...
I'm not really a fainter, this is my 4th and I'm 46. I've only ever fainted when ill before (with tonsillitis as a child, strep throat and norovirus as an adult). Anyone any experience of something similar?