Hi mitsi. I love spicy food! I'm not aware that spices themselves have any negative (or positive) effect on Blood Glucose levels. In terms of health I understand that hot peppers (capsaicin) can be good for the blood circulation. Perhaps if you are not used to curry and ate a Vindaloo, the physical stress might send your BG high but it might more likely be the rice, chapatis and lager used to wash it down
Seriously, for me, I add spices to my food freely without concern for my BGs... what the spices are added to is where you probably need to look. I have heard that Turmeric has anti-inflammatory properties but not sure there is scientific evidence to back it up... it tastes good anyway.
But spices can also be plus by adding flavour to your food... especially if you find you need to adjust your diet to manage BG control.
Did you have a specific example you were concerned about?