The labia minor on one side swelled up like a balloon to the point where it looked like a little sausage, and it seemed that the swelling continued up into my vaginal canal on that side. I don't recall much in the way of itching, just that it was really uncomfortable. This recurredonce, a few months or a year after the first time.
There were no insect bites or anythign in evidence, no changes to laundry detergent or any other thing that would be expected to irritate the area. I had been sexually active, but if I recall correctly, not for a period of time before the first instance. I've never tested positive to an STI, and thanks to wonderful Australian sex ed, brilliantly communicative parents, and an incredibly scary HIV education campaign I've been absolutely religious in my use of condoms since becoming PiV sexually active at the age of 15.