In mechanics, a force is that which causes a change in velocity or, if you prefer, that which causes an acceleration. When more than one force acts on an object it is the net force that is important. Since force is a vector quantity, use geometry instead of arithmetic when combining forces.
Quick Answer. A crawling sensation felt on the skin may be caused by a condition called morgellons, according to WebMD. Common symptoms of morgellons include feeling like bugs are crawling on the skin, burning, itching and stinging sensations. In some cases skin sores may appear as well.
More specifically, the sensation of crawling insects (without actually there being insects) on your skin is called formication. There are a few causes but the one that is most common is alcohol withdrawal. This is important is means someone is close to seizures from alcohol withdrawal -- a deadly situation.