Why do we get butterflies in our stomach?

When you face something stressful or exciting, the body activates its fight-or-flight response, releasing adrenaline. This hormone redirects blood flow toward the muscles and away from the digestive system, and it alters the movement and sensitivity of the gut. The stomach and intestines are lined with a vast network of nerves sometimes called the second brain, which is in constant communication with the head via the vagus nerve. When the brain senses a threat or thrill, these gut nerves react, producing the light, fluttery, or churning feeling we describe as butterflies. It is a normal physical side effect of strong emotion, and the same mechanism explains why anxiety can cause genuine stomach aches or nausea.