Do ear plugs cause infections?

No, ear plugs do not cause ear infections. That is simple and unambiguous.

Putting dirty ear plugs in will cause infections so no taking them out, putting them in a pocket, and then putting them back in the ears unless they are a silicone type and can be washed first.

Dirty hands putting the ear plugs in will cause infections. Having a good scratch of the Gentleman Jewels then getting hold of the ear plug and rolling it about in the fingers and shoving it into an ear will cause infections.

Ear plugs do not cause infections - how someone uses them causes infections.