Hair loss: A good friend of mine, who is only 22 years old, has unfortunately, lost a great deal of his natural hair. Is a wig permissible?

This has somewhat crippled him as a happy, healthy young person. He has looked into various solutions and has considered some replacement procedures. What is Islam's position on this issue? I was reading through one of the various Islamic websites regarding fake hair, and one of the responses went thus: "As to fake hair (not from human source), Muslim scholars have had different opinions about it. Some allow it, others don?t. You may choose the opinion that your heart feels comfortable with." Would you kindly explain the correct stance, if there is one. Thank you very much.