Some people who feel like their skin is crawling suffer from an anxiety disorder. The feeling comes when a person is anxious and their brain sends out a signal telling them something is crawling over their body. Another reason a person may feel this crawling sensation is due to a withdrawal from a substance. This can be drugs, alcohol, or some other type of addictive substance. The nervous system can often make a person feel like their skin is crawling even though nothing is going on.