Neuropathy is unexplained nerve pain felt by individuals.

Nerve pain is caused by damage to the nerve. More than 50 medical conditions, drugs, and toxins are known to cause nerve damage, including:

• Diabetes mellitus
  
• Human immunodeficiency virus (HIV) infection
  
• Celiac disease
  
• Trauma
  
• Amyloidosis
  
• Fabry's disease
  
• Medications, including B6 (pyridoxine), isoniazid, HIV medicines, or chemotherapy
  
• Toxins, such as heavy alcohol drinking
  
• Autoimmune conditions, such as lupus and vasculitis

Once a nerve is damaged, it is more likely to start behaving abnormally. It may become quiet and send no information, which causes numbness. Or it may send excessive and inappropriate pain messages.  WebMD