Regular use of Daily Wormers prevents harmful parasites infestations. Many types of equine parasites live in manure in the grass and are eaten as the horse grazes. Once these parasites enter the horse's system, they migrate, mature and lay eggs. A new generation of parasite eggs and larvae leaves the horse in manure, then waits in the grass to be ingested again. Daily dewormer paralyzes parasites in the digestive tract and moves them harmlessly out of the horse's system.