Hi,
I found some great toe-post Fit-Flops in one of my charity shops for a bargain £3 recently. They fit perfectly and are ridiculously comfortable for my neuropathy-damaged feet (I tend to live in squishy garden clogs, crocs, that sort of thing since BC chemo).
The only problem is that there are these weird white marks on the insole part, where your feet go.
Thought it would prob be dead skin from previous wearer, and that it would come off with some washing up liquid and a good scrub. Used both scrubbing brush and an old toothbrush, nice hot water, and they STILL look kinda manky!
Have looked everywhere online, can’t find anything about about this.
Anyone experienced this? Has anyone got any brainwaves about how to clean them up?
The outer soles show v little wear, the uppers look almost new, so I’m puzzled as to why these white marks seem so ingrained because they don’t look like they’ve been worn much.
Will try to put up a pic for the first time on here, so you can see what I’m waffling about!
TIA for any helpful answers 
JA