Paresthesia is an abnormal sensation of the skin (tingling, pricking, chilling, burning, numbness) with no apparent physical cause. Paresthesia may be transient or chronic, and may have any of dozens of possible underlying causes. Paresthesias are usually painless and can occur anywhere on the body, but most commonly occur in the arms and legs.
The most familiar kind of paresthesia is the sensation known as "pins and needles" after having a limb "fall asleep". A less well-known and uncommon but important paresthesia is formication, the sensation of insects crawling underneath the skin.