Numbness and tingling, sometimes described as the feeling of pins and needles, is usually caused by abnormal function among the nerve endings in the affected area. Most of the time, the effect is benign and temporary. WebMD gives the example of an arm held at an odd angle while you sleep. When you wake up, the arm will likely have a case of pins and needles that clears up quickly.
Sometimes, however, pins and needles can be a sign of something more serious than an awkward sleeping position. If the tingling in your hands or feet is chronic or if it comes and goes, it could be associated with nerve damage. Other symptoms WebMD lists as being associated with nerve damage include pain, itching, and wasting of muscle tissue in the area. This kind of damage is known as peripheral neuropathy, and there are over 100 distinct ways of causing it. Peripheral neuropathy is most common in older people, and afflicts up to 20 million Americans. Diabetes is a common cause of peripheral neuropathy, as are alcoholism, vitamin deficiencies and carpal tunnel syndrome which is often caused by repetitive stresses on the tendons of the hand. Sometimes, however, there is no obvious cause and therefore no obvious treatment.