Evening primrose oil is taken by some people with MS because it contains gamma-linolenic acid, which may have some immune suppressing properties.  Although this potential immune suppression may theoretically be helpful in MS, the studies of gamma-linolenic acid that have been done to date have generally failed to show any benefit on clinical measures of MS. 

MS has a highly variable course from individual to individual and sometimes even from year to year in the same person.  It is therefore impossible to evaluate whether or not a therapy is beneficial based on anecdote only.  A good resource for checking out alternative and complementary therapies used in MS is the book Alternative Medicine and Multiple Sclerosis by A.S. Bowling.  The initial chapters also provide very good background information on how to evaluate health claims.  Many MS Society offices have a copy in their libraries.

Dr. Mary Lou Myles