These mats have a caustic smell that will not go away. I've washed them with assorted soaps and cleaners, vinegar, vanilla water (recommended by mfg), left them in the sun for two weeks between washings, and they still smell. They do not smell like rubber, or plastic, but rather like something living beings should not injest or be around. The smell has diminished, but is not gone. I would like to return these mats, but there is some spotting on one of them from something I've tried to clean them with. My suggestion would be to buy these only if you can see, feel, and smell them before purchase, rather than buying over the internet as I did. This is my first review, ever. I hope it is helpful to someone.