The most common reason for numbness or tingling is a problem with nerve function, either because the nerve itself is injured, something is pressing on the nerve, or an imbalance in the body's chemistry interferes with nerve function.
Numbness and tingling down the arms and legs can also include symptoms such as pain, burning, pricking, or creeping along the skin. These symptoms may indicate a malfunction of sensory nerves.
Numbness into the arms and legs may also be related to malfunction in the nerves located in the neck or lower back. Degenerative disc disease or swollen discs will cause the bones of the spine to put pressure on the nerves coming out of the spinal cord, causing numbness. If you have been in a car accident the resulting neck and lower back injury could be the cause of the numbness you may feel. A proper examination by a professional is required to determine the cause.