Why some people feel their skin itching when they're told about insects and no insects happen to be nearby? Sometimes when people talk in public about cockroaches, for example, it happens for some people to feel the skin itching and yet, no cockroaches were there. Is there a name for this phenomenon?
The name you are looking for is Formication.


  Formication is the medical term for a sensation that exactly resembles that of small insects crawling on (or under) the skin. It is one specific form of a set of sensations known as paresthesias, which also include the more common prickling, tingling sensation known as "pins and needles". Formication is a well documented symptom, which has numerous possible causes.