What causes numbness of the arms and legs?

Many things: Carpal tunnel syndrome is the most common cause of numbness in the hand on the thumb side. Cubital tunnel syndrome causes little finger numbness. If both of the entire hands and feet are numb, then a peripheral neuropathy is more likely. This can be related to long standing diabetes. This problem needs to be worked up by a physician.

Many possibilities: Numbness can occur from various reasons. Some potential causes include vitamin deficiency, nerve damage, nerve compression, alcohol over consumption, side effects of different medications, or as a result of different systemic medical conditions such as diabetes. Get evaluated by a professional to determine the diagnosis. Treatment is based on the diagnosis.