The fleas are having a great time on your pet. Your veterinarian recommends a product that you drip onto your pets back once a month. These are known as spot on treatments and they are insecticides that disrupt the nervous system of the fleas.  All of these products kill the adult fleas and some kill the eggs are larvae too.  If you plan on using spot on products for cats and dogs, carefully follow the instructions and monitor your pets for any adverse reaction.

My older cat, Mollie lost some hair right under her collar where the product was applied. The hair never grew back. Remember that these treatments are pesticides. If you have several pets, separate them after each application to prevent them from licking the chemical off of each other.  By taking the proper precautions, spot on treatments can be a very effective way to fight fleas.