A number of factors can cause neuropathies. When a single nerve is affected, the most likely cause is trauma or some type of repetitive use that puts pressure on the nerve. Nerve pressure can result from using a cast or crutches, spending a long time in an unnatural position — such as typing at a computer keyboard — or having a tumor or abnormal bone growth.

When damage occurs to several nerves, the cause is frequently diabetes. About half of all people with diabetes develop some type of neuropathy. Other common causes include alcoholism, HIV/AIDS, inherited disorders and a deficiency of certain vitamins, especially B vitamins.

Autoimmune diseases, including lupus and rheumatoid arthritis, kidney disease, liver disease and an underactive thyroid (hypothyroidism) also can damage peripheral nerves. So can exposure to poisons, some toxic substances and certain medications — especially those used to treat cancer. You may even inherit a tendency to develop peripheral neuropathy.

Sometimes bacterial or viral infections may cause neuropathy. An acute condition called Guillain-Barre syndrome frequently causes severe damage to all or part of your peripheral nerves by destroying the myelin sheath that covers nerve fibers. The myelin sheath acts as an insulator for your nerves and helps conduct nerve impulses. Although the exact cause of Guillain-Barre syndrome isn't known, approximately two-thirds of cases occur after an infection, surgery or immunization.

Guillain-Barre syndrome destroys the protective covering of the peripheral nerves (myelin sheath), disabling the nerves from transmitting signals to the muscles. If the myelin sheath doesn't recover, ...

Unfortunately, it's not always easy to pinpoint the cause of peripheral neuropathy. In fact, if your neuropathy isn't associated with diabetes, it's possible the cause may never be found.

• Guillain-Barre syndrome

• Hypothyroidism

• Lupus

• Rheumatoid arthritis

• Underactive thyroid

Having diabetes places you at high risk of developing peripheral nerve damage. In fact, about half of people with diabetes have some form of neuropathy. The risk increases the longer you have diabetes, and is highest for those who've had the disease for more than 25 years. Your risk is even greater if you are older than 40 or have difficulty controlling your blood sugar level.

Although researchers don't understand exactly how damage occurs, a high blood sugar level seems to impair your nerves' ability to transmit signals. You can help reduce your risk by carefully following a medically approved plan for keeping your blood sugar level as close to normal as possible.

Your risk of developing peripheral neuropathy is also higher if you have one or more of the following risk factors:

• Alcohol abuse. Excessive drinking of alcohol can affect your nervous system, causing numbness of your hands and feet.

• Vitamin deficiency. A lack of certain vitamins, especially B-1 (thiamin) and B-12. Pernicious anemia, which occurs when your body can't absorb B-12 properly, often leads to peripheral neuropathy.

• Autoimmune diseases. You're more likely to develop peripheral neuropathy if you have an autoimmune disease such as lupus or rheumatoid arthritis, or if your immune system is compromised by the human immunodeficiency virus (HIV) or AIDS.

• Other health problems. Medical conditions including certain types of cancer, kidney and liver disease, also can put you at risk for nerve damage.

• Repetitive stress. A job or hobby that puts stress on one nerve for long periods of time increases your chances of developing peripheral neuropathy. In carpal tunnel syndrome, for example, the median nerve that extends through your wrist into your fingers becomes compressed. Repetitive assembly line work or work involving prolonged, heavy gripping can compress the median nerve. Playing golf, tennis or a musical instrument and using vibrating power tools or even crutches also can put pressure on peripheral nerves.

• Toxic substances. Exposure to some toxic substances can make you susceptible to peripheral nerve damage. These substances include heavy metals, such as lead, mercury and arsenic; organic solvents; carbon monoxide and certain medications, such as those used to treat cancer or AIDS.