Where Else Was This Used?
When it comes to sanitary or pharmaceutical products, you might want to err on the side of safety and purchase these things new. You never know what someone might have used this specific item for before, and you certainly wouldn’t want to obtain some sort of infection.
This second-hand skin buffer that was “mostly used on feet” would be a good thing to steer clear of. We would not recommend sharing a skin buffer with someone that you don’t know. And the fact that you don’t know what this was actually used for is kind of disturbing.