How long does a flea drop remain effective on a cat? - briefly
A flea spot‑on product remains active on a cat for roughly four weeks, providing continuous killing of fleas during that time. Reapply after about 30 days to keep protection effective.
How long does a flea drop remain effective on a cat? - in detail
A flea spot‑on preparation applied to a cat’s skin typically provides continuous protection for a period ranging from 21 days to 8 weeks, depending on the active ingredient and the product’s formulation.
The most common classes of actives are:
- Imidacloprid / pyriproxyfen – 21 days of kill‑and‑prevent activity.
- Selamectin – 30 days of efficacy against fleas, ear mites, and certain parasites.
- Fipronil / (S)-methoprene – 30 days of adult‑flea killing and larval development inhibition.
- Fluralaner – 8‑week protection, covering both adult fleas and immature stages.
- Afoxolaner – 30 days, with rapid kill of adult fleas and interruption of the life cycle.
Key variables influencing the actual protection window include:
- Cat’s weight – manufacturers specify dosage ranges; under‑dosing shortens effectiveness, overdosing does not extend it.
- Hair length and grooming – dense or long coats may retain the product longer, whereas frequent licking or bathing can reduce residual levels.
- Environmental exposure – heavy rain or swimming can wash away surface‑applied compounds, though many formulations are designed to be water‑resistant for up to 48 hours.
- Health status – severe skin conditions or concurrent medication may alter absorption, potentially affecting duration.
Application guidelines that maximize the claimed protection period:
- Apply the entire dose directly onto the skin at the base of the neck, where the cat cannot reach it with its tongue.
- Ensure the skin is dry and free of debris before administration.
- Re‑apply at the interval specified on the label; do not extend the interval based on perceived “still effective” signs.
- Store products at temperatures recommended by the manufacturer to preserve chemical stability.
If a cat shows any signs of flea activity before the next scheduled dose, it may indicate resistance, improper application, or environmental reinfestation, and a veterinary consultation is warranted. Continuous use according to the product’s schedule remains the most reliable method for maintaining flea control.