In article , Tony Cooper
wrote:

Once in awhile I'll get a fingerprint on the lens because I use a
Black Rapid strap with my camera low on my hip and inadvertently touch
the lens when reaching for the camera. In that case, I use a Kodak
lens cleaner solution. I think I've been using the same small bottle
of lens cleaner for at least two years. Maybe longer.

try a lens cap.