A rel=”nofollow” attribute can be added to links to inform search engines to ignore and not follow them. Nofollow links do not pass authority and will therefore not impact search rankings and can be used for both internal and external links. Within our Hangout Notes we cover advice from Google around how they manage this directive with further recommendations for best practice use.
Affiliate links for main affiliate programs are automatically recognised and effectively nofollowed. They won’t cause penalties.
Affiliate links should be nofollowed like any other paid link.