About a month ago, I stayed in a hostel in Spain for 7 days before I realized it was infested with bed bugs. To give you an idea of how bad it was, on the seventh day I had about 60 bug bites all over my body and was able to spot one live bug and three dead bugs (one of which was in my luggage). I was terrified of bringing them into my home so I took all the precautions and then some.
I returned home to Canada a week later. 2-3 days after that, almost all of my old bites started flaring up again in addition to some new-looking ones. I did all the reading that I could about old bites re-flaring up but there just wasn't that much information on the topic, and honestly, not knowing if I brought the bugs home with me was incredibly stressful. I am now certain that I did not bring any into my home because I have not had a reaction in over two weeks nor have there ever been any signs of bed bugs in this house. So now that my nightmare is over, I'd like to share my personal experience and add to the knowledge base, and hopefully calm some peoples nerves!
First off, the cause of my re-flare up was likely lack of sleep and stress. Secondly, I knew which bites were old bites flaring up again because all of my bites will leave a dark brown mark on my skin that can stay for months before they fade completely (see Hyperpigmentation if you want more info).
Now, there were these new-looking bites that were making me wonder if I brought the bugs home with me. I was certain they were new bites because they were not in a place with a dark brown spot, and I remembered counting all the bites I had in this particular area a week before. But I was suspicious about these new bites for a couple of reasons: (1) the new-looking bites were positioned alongside some of my old "rows" of bites, so they looked like they would have been bites from the same sitting. And (2) they didn't look the same as my initial bites, they were definitely smaller and they didn't have the "target" shape that many of my initial ones had.
This is my theory on the new-looking bites, which is based off something I read earlier in a comment on this forum: The new-looking bites are actually old bites that I just never reacted to before, but having all of my bites re-flare up due to stress triggered a reaction to those old non-reacting bites. I guess this could be considered a delayed reaction, but I have heard of flare ups happening weeks or months after the initial bites, and I would not be surprised if old non-reacting bites flared up at this time as well.
So that's my story! Please let me know if anyone else has had the same or different experience. I believe this theory is correct and would love to get some confirmation.