Such symptoms are consistent with exposure to elemental mercury, the liquid or "quicksilver" version of mercury sometimes used in thermometers. According to the Cleveland Clinic, this form of mercury is "usually harmless if you touch or swallow it because its slippery texture won’t absorb into your skin or intestines." But if you breathe in any of it, watch out—symptoms occur "immediately" and can include coughing, breathing trouble, nausea, bleeding gums, and a "metallic taste in your mouth."