Advantage Flea & Tick Treatment Cat 1-9Lb 6 Month Supply kills 98 – 100 percent of adult fleas within 12 hours of application. And it kills reinfesting fleas within two hours. One convenient application of Advantage keeps working for up to a month. Advantage Flea & Tick bites can cause discomfort for your pet, lead to skin infections, lead to allergic skin reactions causing irritation and can even transmit other disease-causing organisms, including tapeworms.