The bioflavinoid quercitin has antihistaminic effects and may help some pets.    From Wordnik.com.  [Dr. Richard Palmquist: Does Your Pet Have Allergies?] Reference

Rutin is a bioflavinoid which composes 4-6\% of buckwheat.    From Wordnik.com. Reference

Rutin, a citrus bioflavinoid naturally occuring in the rind can significantly increase vitamin C absorbtion, lower cholesterol and do other cool stuff for you.    From Wordnik.com.  [Original Signal - Transmitting Buzz] Reference