How long do flea and tick drops remain effective? - briefly
Topical flea‑and‑tick medications usually provide protection for approximately four weeks after each dose. Duration can differ based on the specific formula, animal weight, and exposure to water or heavy activity.
How long do flea and tick drops remain effective? - in detail
Flea‑and‑tick spot‑on treatments work by spreading across the skin surface after application. The protective window depends on the active ingredient, formulation, animal size, grooming habits and exposure to water or shampoo.
Typical residual periods
- Fipronil‑based products – maintain killing activity for 30 days; some brands extend to 45 days with a higher dose.
- Imidacloprid + flumethrin – effective for 30 days; a few formulations claim 42 days under controlled conditions.
- Selamectin – provides 30 days of protection against fleas, ticks, heartworm and some mites.
- Fluralaner (e.g., Bravecto) – single dose lasts 12 weeks (84 days) for both fleas and ticks.
- Afoxolaner (e.g., NexGard) – 30 days of efficacy; some extended‑release versions reach 45 days.
- Sarolaner (e.g., Simparica) – 30 days; a 60‑day version is available in certain markets.
Factors influencing duration
- Hair length and density – thick or long coats may slow diffusion, reducing surface concentration.
- Bathing or swimming – washing within 48 hours after application can remove a portion of the product; subsequent baths may shorten the protective period by up to 10 days.
- Weight class – under‑dosing a large animal with a formulation intended for a smaller weight range lowers efficacy duration.
- Environmental temperature – high heat can increase skin oil production, potentially accelerating absorption and shortening the residual window.
- Resistance development – repeated use of the same active ingredient may select for tolerant flea or tick populations, diminishing effectiveness before the labeled period ends.
Reapplication guidance
- Apply the next dose no later than the end of the stated protection window; for products with a 30‑day label, re‑treat on day 28 to allow for slight variations.
- For extended‑release formulations, follow the specific interval (e.g., 84 days for fluralaner) and avoid overlapping doses.
- If the animal has been bathed or exposed to heavy rain within the first two days after treatment, schedule the next dose according to the original interval; do not apply an extra dose.
Monitoring effectiveness
- Conduct a flea comb check weekly; presence of live fleas after the expected kill‑time indicates possible premature loss of activity.
- Tick counts after outdoor exposure should be performed within 24 hours; persistent attachment suggests reduced efficacy.
In summary, most monthly spot‑on products protect for roughly one month, while newer oral and topical formulations extend protection to 8–12 weeks. Adjustments for coat type, bathing frequency and weight ensure the stated residual period is achieved.