4 yr old obsessive need to change underwear

I have a 4 year old son who just recently has a need to constantly change his underwear.  It started about 3 weeks ago when he was sick with a cold and accidentally wetted his underwear in the middle of the night.  Since then, he has complained that his underwear is wet in the middle of the night and would get up around 4am to change his underwear.  It would happen a couple of times the first 2 weeks.  Now it's happening every night.  His underwear is not wet.  I've tried explaining it to him, showed him that it's not wet, etc.  He goes from saying that it's wet to saying that it "itches" him.  But now, I've caught him changing his underwear during the day when we're home too.  I've brought it to the attention of our pediatrician and he's checked for infection and hasn't found any problems.  I'm at my wit's end.  I don't know what to do anymore.  It sounds like it's a psychological issue but I don't know how to "fix" it.  Do I just let it be and not make a big deal out of it in hopes that he'll outgrow it?  HELP!

Thanks,

[Kevin Kennedy, Ph.D.]

Absolutely just let it go - it will resolve itself over time. Regard the behavior as 'not a problem'. There really is nothing you need to do about this.