Anti-fatigue mats are almost exclusively created using rubber or latex. And some are created from a 'gel' that is a bit suspect. It is the plasticizer in the rubber/latex products that will do the most amount of damage.

There are heavy area rugs (either well built or so large that they are heavy) that have natural backings or woven backings (nothing to indicate an anti-slip product) will be just fine. There are excellent rug pads that will do very well underneath area rugs. These look like a felted or matted appearance (often a weird gray colour). These are the types of rug pads you want to look at.

If in doubt, do not purchase. There are many companies that produce rugs that are 'safe for use with hardwood'. These are often safe for use with vinyl. How is that you ask? Because most vinyl floors are finished with a coating of urethane or polyurethane...just like hardwood.

Here's a hint...Ikea sells rugs/pads with this designation but places like Target do not. You want to focus on 'mid-range' shops or higher. Entry level products are most likely a no-no. You really do want to see a tag that states "Safe for Use with Hardwood Floors". That's where I would start.

Thank you SJ!