13 Herbal Wormer for Canines - 90 CapsuleCommercial synthetic dog wormers can have undesirable side effects, and only work against certain types of worms, with no effect at all on protozoa and some other harmful parasites. In contrast, #13 Herbal Wormer naturally supports your dogs natural defenses against worms, because when its operating correctly, that defense system is enough to destroy or expel unwanted parasites. This formula is not intended to replace heartworm preventative