Is this the game skin or a default replacement? Did you have default replacements, but remove them? I know sometimes this can happen if you install default replacements or remove them, but it doesn't update correctly. Even if that's the game skin, I do have some suggestions that may help.
Take your Sim to a mirror and change their eyebrows. If that doesn't do it, go into your Sims 2 folder and delete cache files and thumbnails. If that doesn't fix it, I suggest getting the ffs lot debugger (aka batbox). Then try Fix- tans and burns.