It is possible that the smell of the garlic is only triggering panic symptoms. Weed used to do this to me, though it wasn't dropping blood sugar. It was just panic.
However, insulin is released in response to the smell of food as the body prepares to digest whatever you're smelling. So it is possible, also, if your insulin and adrenals are screwed up for this to actually have happened.
I don't recommend consuming the garlic by the way. The allicin in the garlic lowers blood sugar. This is why it is recommended so much for diabetic patients.