Health anxiety is a fear and preoccupation with the belief that one has, or is in danger of developing, a serious illness like cancer, ALS, or a heart attack. It involves the misinterpretation of normal bodily sensations as dangerous. Healthy bodies produce all sorts of physical symptoms that might be uncomfortable, painful, unexpected, and otherwise unwanted — but not dangerous.
Normal physical symptoms that often produce fear and worry include changes in visual acuity, heart rate and blood pressure, saliva levels, depth of breathing, balance, and muscle tone, to name a few. When a person misinterprets a new growth on the skin, a headache, a muscle twitch, or change in bowel movement color as a sign of a fatal disease it creates undue worry. The physical sensations are real, but they are not necessarily symptoms of a fatal disease. Many people with health anxiety are often unable to function or enjoy life due to their fears and preoccupations.