Headlights Cloudy? Here's the Real Cause (It's Not Dirt)

If your headlights look hazy or yellowed no matter how much you wash the car, washing isn't the fix — the problem isn't on the surface in the way you'd expect.

The real cause

Modern headlight lenses are polycarbonate plastic, not glass. Polycarbonate is genuinely vulnerable to UV light over time — years of sun exposure slowly oxidises the outer layer, turning it hazy and yellow from the inside of the material itself, not from dirt sitting on top. That's exactly why a wash — even a thorough one — never fixes it.

The real fix

You need a real headlight restoration process — light abrasion to remove the oxidised layer, followed by a UV-protective sealant so it doesn't just oxidise again in a few months. This is a genuinely different product category from general polishing (which is designed for painted clear coat, not polycarbonate).

Real MOT relevance: cloudy headlights can genuinely affect how well your lights actually illuminate the road — worth checking before an MOT, not just for looks. See the MOT page.