Stress can be contagious through sweat and trigger physiological stress responses in people nearby via cortisol transmission as secondhand stress.
Stress can be contagious in a very literal sense. When we experience stress, our bodies release cortisol, the primary stress hormone, which can be emitted through our sweat.
This cortisol can then be absorbed through the skin of people nearby, potentially triggering a physiological stress response in them.
The phenomenon is similar to how women's menstrual cycles can synchronize when they're in close proximity.
This also relates to Emotional Contagion I noted before. "The reason we say "don't be upset" is often because we don't want to have our emotions synchronized and be upset."