They can detect carbon dioxide, so if you are breathing heavily (fearfully), I suppose they could detect that. There was a spot on my gloves that used to get repeatedly stung. I think a bee probably daubed alarm pheromone on it in a larger than usual quantity. A bit of a scrub with Pink Miracle saddle soap cleaned it up and now they largely ignore my gloves.
After a few decades of beekeeping, I have not found my bees to be reliably docile enough to go without protective gear. I also have very sensitive skin, and tend to get a more vigorous local reaction than most. For example, I was stung on my neck a couple of weeks ago, and had swelling and redness over an 8" area. Needed to cover it up with a light scarf for a few days! So generally I try to avoid being stung by suiting up and being gentle. I will never trust them, though.