From Dr. Hale's website:
Olopatadine is a selective H1-receptor antagonist and inhibitor of histamine release from mast cells. It is used topically in the eye. Kinetic studies by the manufacturer suggest that absorption is low in adults and that plasma levels are undetectable in most cases( <0.5 ng/mL).[1] Samples in which olopatadine was found in the plasma compartment were at 2 hours and were < 1.3 ng/mL. Because adult plasma levels are so low, it is extremely unlikely any would be detectable in human milk. No data are available reporting levels in human milk but the risk is probably quite low.
Tom Hale Ph.d.