How long after applying drops to the neck do fleas die? - briefly
Fleas generally die within 30‑60 minutes after the neck‑applied drops are absorbed. The exact time may vary slightly with product concentration and the animal’s skin temperature.
How long after applying drops to the neck do fleas die? - in detail
Applying a spot‑on flea medication to the nape of a pet initiates a rapid toxic effect on adult fleas. Most products that contain fipronil, imidacloprid, or selamectin begin to incapacitate adult fleas within 4 – 6 hours of contact. Complete eradication of the adult population on the host typically occurs by 24 hours, with many formulations achieving 95 % kill in the first 12 hours.
Factors influencing the exact interval include:
- Active ingredient – fipronil and imidacloprid act faster than some newer compounds.
- Dosage relative to body weight – correct dosing ensures optimal plasma concentration.
- Flea resistance – populations with documented resistance may require longer exposure.
- Stage of the flea – eggs and larvae are not directly affected; they die when the environment is cleared of adult insects.
After treatment, observe the animal for residual movement of fleas. If live fleas are still seen after 12 hours, re‑examination of dosage and product choice is advisable. Environmental control (vacuuming, washing bedding) remains necessary because the medication does not affect immature stages present in the home.