1998 avolon windows fogging up?????

Please help. I have a 1998 toyota avolon with 105,000 miles. The windows fog up bad in the cold weather (Indiana). Is it because of the humidity inside the car. I notice when the selector switch is in the defrost position for the front window the ac automatically comes on. Is there a filter of some kind that I need to replace? The temperature and vent selector switch work fine. Any input would be great. Thanks

They need washing. There is anti-fog stuff you can buy but I don't use it. If you smoke in the car they will fog more.

You can eliminate allot of the fog on the windows by choosing the 'fresh' air option on the climate control.