How long after applying Stronghold do fleas die? - briefly
Fleas typically start dying within 12 hours of a Stronghold dose, with the majority eliminated by 24–48 hours. Adult insects are usually cleared from the host within that time frame.
How long after applying Stronghold do fleas die? - in detail
Stronghold (imidacloprid + moxidectin) is a topical spot‑on treatment applied to a dog’s skin. The product absorbs through the hair coat and reaches the bloodstream, where it targets the nervous system of adult fleas. Contact with the drug begins immediately after application.
- Within 30 minutes: fleas that land on the treated animal experience paralysis and start to die. Laboratory data show >50 % mortality at this point.
- At 4 hours: mortality rises to approximately 80 %.
- By 8–12 hours: most adult fleas on the host are dead; the majority of the population is eliminated.
- At 24 hours: virtually all adult fleas present at the time of treatment are killed.
- Within 48 hours: the life‑cycle interruption is complete, preventing newly hatched fleas from surviving.
The rapid action is due to imidacloprid binding to nicotinic acetylcholine receptors, causing overstimulation and paralysis. Moxidectin contributes to killing immature stages (larvae, pupae) that may be ingested during grooming. The residual effect lasts up to four weeks, protecting the animal from re‑infestation during that period.
Therefore, the initial kill phase occurs within half an hour, with near‑complete elimination achieved by the end of the first day and full cycle control by two days after treatment.