Thank you, Kathleen.
It's only happened 4 or 5 times, thankfully, and seems to follow a disturbed night - last night, I woke up feeling very hot and nauseous, and then my heart racing woke me up at just after 6am with adrenaline as well.
I have a headachey feeling now (I rarely get headaches usually).
Thanks Briony. Fortunately, it only seems to happen just after I get up and go downstairs. I have to clear my throat, and then it starts. Lasts a few minutes, eyes streaming, and then it passes. My poor dogs were desperate for their breakfast, barking at me as I was bent double over the kitchen sink!