Twitchings have a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons. Even medications like anticholinergic drugs such as benadryl can cause them. Stimulants like caffeine and amphetamines can cause them directly. If it persists you can see a neurologist to rule out lower motor neuron disease. To read more about them, you can follow this link - http://en.wikipedia.org/wiki/Fasciculation. Thanks.
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