Is this a problem on your car? Have you tried to fix it and it just not seem to ever dry out inside. In his video Kent Bergsma discusses possible reasons why your headlight may be building up moisture inside, and then demonstrates what he does to fix the problem on his own W220 chassis S500 Mercedes sedan. This is a common problem on many cars and the principles apply to many.
This can happen on a number of models for a number of reasons