How long does Frontline remain effective against fleas? - briefly
Each application of Frontline protects against fleas for roughly 30 days. Re‑application each month is required to maintain continuous efficacy.
How long does Frontline remain effective against fleas? - in detail
Frontline’s flea‑killing action lasts for about 30 days after a single dose. The product contains fipronil, which kills adult fleas on contact, and (S)-methoprene, an insect growth regulator that prevents eggs and larvae from developing. Together they provide continuous protection throughout the month.
Key points that influence the 30‑day window:
- Application site – the solution spreads over the skin and coat; thorough spreading ensures full coverage.
- Animal size and weight – dosing is calibrated to body mass; under‑dosing reduces the protection period.
- Water exposure – bathing or swimming within 24 hours can wash away the chemicals; after that, the barrier remains intact.
- Season and environment – heavy flea infestations or warm, humid climates may increase pressure on the product, but the formulation is designed to maintain efficacy for the full month under normal conditions.
- Health status – skin disorders or excessive oiliness can affect absorption, potentially shortening the effective period.
For optimal results, reapply the treatment every 30 days. If a pet is in a high‑risk setting—such as a multi‑pet household, a kennel, or an area with severe flea problems—some veterinarians recommend a two‑dose schedule spaced two weeks apart, followed by monthly maintenance.
When the product is used on cats, the same 30‑day duration applies, but only Frontline Plus for cats is approved; using the canine formulation on cats is prohibited. Dogs receive the same protection timeline, with formulations available in spot‑on, chewable, and spray forms; all share the month‑long efficacy claim.
Resistance monitoring shows that fipronil‑based products retain activity against most flea populations, but emerging resistance in certain regions can reduce the effective period. In such cases, rotating to a different class of flea control (e.g., isoxazolines) may be advised.
In summary, a single application provides continuous flea kill and development inhibition for roughly one month, provided the dose matches the animal’s weight, the product is applied correctly, and the pet is not excessively exposed to water or conditions that compromise absorption. Re‑treatment at 30‑day intervals sustains protection.