A tremor is a type of involuntary shaking movement. Involuntary means you shake without trying to do so. A tremor is often most noticeable in your hands, but may affect any body part (even your head or voice).

There are three main types of tremors:

• Resting or static tremors occur when your hand or affected body part is at rest.
• Kinetic and intention tremors occur when you are moving your hand or affected body part when you are doing something like pressing a button or touching the tip of your nose with your finger. The tremor will usually disappear while the affected body part is at rest.
• Postural or action tremors occur when you are holding your hand or affected body part in a particular position for a period of time. This may happen when you are writing, holding a cup, or when you stand up straight.

Tremors can happen at any age but tend to be more common in older people. Everyone has some tremor when they move their hands. Stress, fatigue, anger, fear, caffeine, and cigarettes may temporarily make this type of tremor worse.

However, a tremor that does not go away over time may be a sign of an underlying medical problem and should be evaluated. You may learn that your tremor is perfectly normal, but eliminating medical reasons for the shaking is important.

Essential tremor is the most common tremor. It is rarely seen when the hands are not being used. It becomes most apparent when you are trying to do something, such as reaching for an object or writing. It is not caused by an underlying disease. This type of tremor may also run in families.

Tremor may be caused by:

• Too much coffee or other caffeinated drink
• Excessive alcohol consumption, alcoholism, or alcohol withdrawal
• Stress, anxiety, or fatigue can cause a postural tremor
• Normal aging
• A variety of drugs and prescription medicines
• Low blood sugar
• Parkinson's disease -- a classic cause of a resting tremor that is often accompanied by slowness of movement, muscle rigidity, and an abnormal gait
• Multiple sclerosis -- can cause an intention tremor
• Other brain, nerve, or movement disorders, including dystonia and certain inherited peripheral neuropathies (such as Charcot-Marie-Tooth disease)
• Overactive thyroid -- can cause a postural tremor
• Stroke
• Brain tumor