Clear and honest communication.

Preferably if possible well before, if we are talking about in a relationship/friendship/coworker. Most people can empathise. But empathy is ultimately based on our own experiences because that’s all we know of, and this goes for all feelings.

Even if the person is not aware of your responses to what ever situation it might be, but it is one that “triggers” a stress response etc. As Clear and concise communication as possible in the situation is always best. But I would refrain from framing the persons unconscious behaviours or normal bodily functions in a way that makes the person feel responsible. Unless they have actually tried to agitate. Since their response most likely would be a defensive one, and thus not helpful for the situation and future dialogue.

So my recommendation would be something along the lines of: I’m feeling really stressed right now and need to collect my thoughts. I need a moment alone.

And try to leave the situation if you can, before asking others to leave.

Try to use broadly relatable language such as stress and anxiety. If it is a person that is not familiar with your need and responses, to help them empathise.

This isn’t a silver bullet, but it will lessen the risk of confrontational responses.