There is no limit regarding age, size or medical conditions. One disc per 80 lbs. Successfully protecting over 44 million pets in 197 countries worldwide.
Common anti-parasite products contain highly unpleasant insecticides (such as pyrethroid). Furthermore, the pharmaceutical industry makes stronger flea and tick toxicants yearly because of the fact that parasites adapt rapidly, becoming progressively resistant.
Once applied to the pet, these chemical substances get into the blood stream via skin pours, by being inhaled or swallowing, and then they then linger in the pet's liver cuasing very grave health issues, even cancer.
Each year thousands of pet deaths caused by unfavorable responses to chemical flea and tick products are reported to the EPA.