That yellowing on your clear case is not dirt. It is oxidation — UV light slowly breaking down the polymer chains in TPU plastic. Once it starts, you cannot fully reverse it.

How to slow it down

  • Avoid leaving the phone face-down in direct sunlight
  • Wipe down weekly with mild soap and water — never alcohol-based cleaners
  • Store the phone case-on, not bare, when not in use

The premium solution

Higher-end clear cases use UV-stabilized TPU or shatterproof polycarbonate. They cost 2-3x more but stay clear for 18+ months instead of 6.