They work by killing fleas and ticks (and sometimes mosquitos, depending on the product) by depositing chemicals into the sebaceous glands, where the active ingredient is released and translocates through the glands that lubricate a cat or dogs coat with oil.

How long does it take flea treatment to work?

Like many things in life, it's not as simple as that! Modern flea treatments, such as FRONTLINE, don't work by stopping fleas from jumping on your pet- they are effective at killing newly arriving fleas within 24 hours.

How does spot on flea treatment work?

Spot on medicines work as an insecticide that kills off fleas on your cat or dog. Once you apply the treatment, the natural oils in their skin distribute the substance around their body. The pesticide chemical in the treatment remains in their hair follicles and continues to be release after the initial application.