While the exact cause of MS is unknown, most researchers believe that the damage to myelin results from an abnormal response by the body’s immune system. Normally, the immune system defends the body against foreign invaders such as viruses or bacteria. In autoimmune diseases, the body attacks its own tissue. It is believed that MS is an autoimmune disease. In the case of MS, myelin is attacked.

Scientists do not yet know what triggers the immune system to do this. Most agree that several factors are involved, including:

• Genetics
• Gender
• Environmental Triggers
  [Possibilities include viruses, trauma, and
  heavy metals ( toxicology)]

For more information

• Allergies
  There is no evidence that an allergic reaction to a specific environmental allergen is involved in triggering MS.
  
• Autoimmune Disease
  MS is widely held to be an autoimmune disease, meaning that the immune system is reacting against a component of the normal antigens in the body as if these antigens were foreign.
  
• Clusters
  Clusters of MS are of interest because they may provide clues to environmental or genetic risk factors, which might cause or trigger the disease.
  
• Etiology
  The study of all factors that may be involved in the development of MS.
  
  
• Myelin
  A substance rich in protein and lipids—fatty substances—that forms layers around the nerve fibers and acts as insulation.