The connection between stress and skin rashes has been the topic of much study. At the root of these connections is the hormone cortisol. During periods of increased stress, cortisol levels rise significantly, which decreases the skin’s barrier function and increases the sensitivity of nerve fibers in the skin. It also causes mast cells to release histamine and cytokines, which translates to itching, redness, and swelling. If you have pre-existing skin conditions, stress can worsen symptoms or cause more flare-ups.