Will give a couple of examples.
Last month I had conjunctivitis for the first time. It freaked me out because it came on throughout the course of a single day and the thought of waking with my eyes stuck closed was scary. I used the drops my doctor had prescribed DD when she'd had it a couple of weeks before, and after I used them I pondered the danger of using someone else's meds and quickly became overwhelmed with a sense of dread, numbness in mouth, quickened heart rate and fast breathing etc. I got up very quickly and paced about a bit, sat somewhere else with my head in my hands to try and calm myself and actually considered asking DH to call an ambulance (was convinced for a moment I was going into anaphylacyic shock and was going to die).
It happened again tonight when I ate some ice cream with walnuts in - it occurred to me that I might be allergic to nuts (no reason to think so, other than its a common allergy) and the same symptoms happened again.
DH thinks it's just exhaustion (we have a 10 week old plus two older ones) but the fear is overwhelming, I feel kind of swamped by it and out of control even though I'm aware I look calm on the outside. For some reason I've developed a real fear of allergic reactions just recently. I've always had an anxious nature and had CBT a few years ago for it.