Thumb numbness can be caused by pressure on a nerve. Another possible cause is an inflammation at the thumb's base if only the thumb is numb, explains MailOnline. Numbness in the thumb can also occur if you move your thumb repeatedly throughout the day by typing or holding a mouse.
Numbness in the thumb is also a possible sign of carpal tunnel syndrome, also known as CTS, according to the Arthritis Foundation. If fingers other than your thumb are numb, you may have CTS. Other signs of CTS are burning and tingling in the hand.
Numbness in the thumb is most often caused by the peripheral nerve being compressed. It is not a dangerous condition in and of itself. If numbness in your thumb is persistent, you might want to get an evaluation from a physician. One other sign numbness could be a serious problem is if it is accompanied by symptoms such as weakness. One common type of numbness is paresthesia, known as the "pins and needles" feeling, which usually occurs after a part of the body falls asleep, notes Dr. Peter Pressman for About.com. Another type of numbness is a total lack of feeling. The severity of the problem depends on the part of the thumb affected.