Chad HigginsIt is time for my annual headache as I try to decide which of the many good flea products to carry and recommend for my patients. Some of the older products definitely donâ??t work as well as newer products. Any product that works to kill adult fleas will eventually not work as well. Fleas, like all other insects, know how to adapt. Any insecticide used year after year will eventually produce a population of insects resistant to it. A recent example would be Frontline, which for many years was a great flea product. A couple of years ago I had several clients using it that developed a severe flea problem. Any insecticide that kills adult fleas will eventually produce fleas that are resistant to it. As I was working on trying to decide which flea products to carry and recommend, I was reminded of an â??oldâ?ť product that has been around for many years. It works just as well as it always has because it is extremely unlikely fleas will become resistant to it. I have stressed repeatedly that fleas can develop resistance to any product that kills adult fleas. This older product doesnâ??t kill adult fleas.Sentinel is a monthly pill for dogs that contains two products. Milbemycin oxime works great as a heartworm prevention, but also controls roundworms, hookworms, and whipworms. The other product is lufenuron which suppresses flea populations by breaking their reproductive cycles. This is why it would be extremely hard to develop resistance to it. If it stops reproduction, fleas canâ??t be produced that are resistant to it. Lufenuron breaks the flea life cycle at a couple of different points. It only needs to break the life cycle at one point to prevent a flea infestation, but the fact that it breaks the life cycle at two points makes it extremely effective to treat an environment already infected.Lufenuron works by inhibiting the development of chitin. Chitin is the hard, crunchy, outer, protective covering of insects. When you give your dog Sentinel monthly to prevent a flea problem, it works by making certain that if a flea gets on your dog it canâ??t reproduce. In order to reproduce a flea must take a blood meal which will contain the lufenuron. Eggs can be produced and fall off the dog into the environment, but that is where the cycle stops. In order for the larvae to get out of the eggs they need to use an egg tooth to break through the shell. It just so happens that the egg tooth is normally made of chitin. No chitin means no egg tooth. Eventually the egg just dies. If you already have a flea infestation, it isnâ??t too late for Sentinel. Using Sentinel along with a product to kill adult fleas is the fastest way to get the problem under control. Studies show that even in severe flea infestations, use of Sentinel monthly along with a product to kill the adult fleas will control the situation within eight weeks. Sentinel not only will prevent any newly produced eggs from hatching as described previously, but it also kills the larval stage of the flea. The larvae must feed on the dried blood (flea dirt) fleas produce when they get on a dog, and this dried blood contains lufenuron. The larvae are covered in chitin for protection and when they can no longer produce it, they die. So in infestations, where eggs and larvae make up 85 percent of the total flea infestation, Sentinel will stop all of these future fleas from becoming adults and reproducing.Using Sentinel for flea control is 100 percent effective at preventing a flea infestation. Although a dog may pick up some â??hitchhikerâ?ť fleas, your home will be protected from an infestation and you can control the â??hitchhikersâ?ť with an occasional dose of one of the many products that kill adult fleas. Using these products only when needed will also make it much harder for fleas to develop resistance to them. Sentinel is also less expensive than the other flea products, especially when you take into account that you donâ??t need to buy heartworm prevention since it is included in the Sentinel.For all of the cat owners out there who feel left out, lufenuron is available for cats in an injection called Program that lasts for six months. Although it doesnâ??t protect against heartworms and intestinal parasites like some of the other cat flea products, it will prevent a flea infested house. Ask your veterinarian about Sentinel for dogs and Program for cats. They are two oldies, but goodies.Chad Higgins has owned Amanda Animal Hospital for the past 14 years. He sees dogs, cats, ferrets and other little furry critters.