What is causing my headlight glass (plastic) to become all scuffed and opaque?

[John DiFool]

2006 Honda Civic SI. I also see this on numerous other cars in this area (Florida)-are they oxidizing or something? IIRC we had a lot of heavy rain last year, a lot of water got inside the headlight bays, and that is when I seem to have first noticed it. Now some white stuff has dripped down into them as well. The local car wash will clean and polish them (including grinding the plastic) for $60 bucks, just curious why this happens...

[KneadToKnow]

Nothing to address the question, but FWIW, you can get a do-it-yourself kit at the auto parts store and do their $60 job for like $20.

[runner pat]

Road grit and exposure to the elements.

[barbitu8]

Headlight lens cleaner for a couple of bucks at auto stores, Walmart, etc. Won't help any discoloration inside the lens, though.

[Mind's Eye, Watering]

UV light from the sun is a big culprit.

From Consumer Reports:

Ultraviolet radiation from the sun is the primary culprit in the headlight aging process, compounded by other environmental factors. The problem tends to be most serious in warmer, sunny climates, but we've seen plenty of evidence of it in northern regions, including on employee cars in our own Yonkers, N.Y., parking lot.

Consumer Reports recommends the Sylvania Headlight Restoration Kit ($21) or the 3M Headlight Lens Restoration System 29008 ($15) to restore the clarity to headlight lenses.

[GaryM]

I used the 3M kit, bought at Harbor Freight, on my 2007 Ford with excellent results.

[obbn]

I used the Measured kit that I purchased from Wally World for about $25. Took about an hour and the results were amazing. The lights would have looked brand new but some of the fading occurred on the inside of the plastic with no way to access it. Other than that it was a night and day difference.