Why does Rudolph's nose glow red?

I believe that every year on Christmas Eve Rudolph shines his red nose to clear the foggy skies for Santa. I mean how else would he be able to see?

Another view:

Rudolph was born that way, so Rudolph and the other reindeer thought it was a birth defect. They made fun of him because of his red nose and wouldn't play with him, even though Rudolph couldn't help it that his nose glowed red. This made Rudolph very sad, having all the other reindeer making fun of him, and no one to play with. I guess reindeer can be like kids (and adults), thinking that just because someone is different that they aren't "as good".

But then, when they realized what a speciall gift his red nose was, and how his glowing red nose could help guide the sleigh, Santa chose him to lead the other reindeer. That was when Rudolph and all the other reindeer realized that being different was not a bad thing, but was actually a good thing.

They all learned that just because someone is different doesn't mean they aren't just as good as every one else is. And now they don't make fun of others who are different anymore, either. They learned that everyone is special in their own way.