Xeljanz: Treatment for arthritis grows a full head of hair for man who was bald due to Alopecia

Researchers may have accidentally found an answer to one life's biggest mysteries: the elusive cure for baldness.

A man went from completely bald to having a full head of hair in just months.

It’s all thanks to a little pill meant to treat arthritis.

But, how does it work - and could the treatment do the same for others?

Kyle Rhodes was bald, but now his hair is thick and full.

"I've gotten a lot of comments about how great my hair is coming in and what a lovely color of hair it is. I find myself a lot of times just playing with it," Rhodes says.

What was the trick?

No, not Rogaine or Propecia - they grow hair only on parts of the scalp.

It was a pill, a drug called Xeljanz that's actually already on the market for, of all things, arthritis.

Kyle's doctor at Yale University decided to give it a try and eight months later, viola! 

Kyle, who's 25, starting losing hair all over his body at age two because of an unusual form of Alopecia.

"Neighborhood kids at school, just jokes, rogaine comments. One thing I did get when I was completely bald is called a skinhead, which I found very offensive," Rhodes recalled.

But now, even his eyelashes and eyebrows are back.

Six and a half million people have a skin disease like Kyle's.

His doctor says the drug may one day help them, too.

But what about the tens of million of men who've just gone bald as they've gotten older?

The doctor doesn't think the drug will help them.

But he does think it's worth doing a study to find out.

The drug can have serious side effects.

Kyle hasn't had any, and he's enjoying his new head of hair.

"I've always wanted an 80's hockey mullet so maybe going towards that," he jokes.

Why would an arthritis drug help hair loss?

The doctor thinks it's because arthritis and some forms of alopecia are related to the immune system.

The drug is not cheap.

Without insurance it can cost can estimated $25,000 a year.

Rhodes said his insurance pays for most of the cost.