Nofollow tags tell search engines not to pass ranking value through a link. For affiliate links, it is usually better to use nofollow because you are linking for business reasons, not to recommend content naturally. This does not hurt your SEO. In fact, it keeps your site safe from penalties. You still get traffic and commissions, but search engines understand the purpose of the link. It is a simple step that protects your site in the long run. Do you apply nofollow to all links or only some?