Essential tremor is a nervous system disorder (neurological disorder) that causes a rhythmic shaking. Essential tremor can affect almost any part of your body, but the trembling occurs most often in your hands — especially when you try to do simple tasks, such as drinking from a glass, tying shoelaces, writing or shaving. Essential tremor may also affect your head, voice, arms or legs.
Although usually not a dangerous condition, essential tremor worsens over time and can be severe in some people. It isn't caused by other diseases, although it's sometimes confused with Parkinson's disease. Essential tremor can occur at any age but is most common in people age 40 and older.