This particular case happened back in 2007, so I'm not sure it's still relevant, but the cheap walmart flip flops have been known to cause chemical burns. I got an email this morning about it, snoped it, and found this.
https://www.snopes.com/medical/toxins/flipflop.asp
If you go to her website, which is linked in snopes, just be warned that her pictures are very cringe-worthy.
Married 11/24/07
Camille Rae 8/21/10
Thea Grace's EDD 5/22/14
Re: PSA: Wal-Mart Flip Flops...