Numbness in the hands (regardless of whether it is the right or left hand) suggests either a problem with the nerves or the circulation. If the numbness is only on one side, it makes it more likely than the problem is with the nerves that actually enervate the right hand as opposed to a problem in the brain or spinal cord. Otherwise, numbness in the right hand can be caused by a lack of circulation. Numbness in just one hand can be caused by trauma or swelling to the nerves in that hand or from a systemic disease that can affect the nerves, but happens to only be causing symptoms in just one hand (for the purpose of this article, the right hand).
A "local" problem is one in which there is a specific injury or condition affecting the nerves in the hand. Any sort of trauma that damages the nerves of the right hand, for example, or causes swelling around those nerves can result in numbness of the right hand. There are many different kinds of injuries that can cause this sort of problem, including broken bones, deep cuts or a bruise or swelling that affects the nerves. Sometimes this trauma can occur in the upper arm, which is where a network of nerves called the brachial plexus is located. In other cases, the nerve problem can occur with the wrist, such as with carpal tunnel syndrome. With carpal tunnel syndrome, the tendons that control muscles within the hands can become swollen due to overuse, which can cause the nerves that carry information from the hand to become pinched, leading to hand numbness.
Because the hands have so many sensory nerves that supply them (especially the fingertips), systemic problems that can cause nerve damage will often first be noticed in the hands. If only one hand is affected, it can just be due to the fact that one side of the body has been more affected than the other. Diabetes, for example, often causes poor circulation in the extremities of the body, which can lead to numbness in the hands and feet. Another disease, lupus, is marked by the immune system attacking normal tissue, including neural tissue. As a result, lupus can lead to numbness in the right hand. Finally, some problems with circulations and blood cells, such as pernicious anemia, can lead to numbness in the right hand.