When do flea and tick drops start to work? - briefly
Flea‑and‑tick spot‑on products start killing fleas within 4–6 hours after application. They begin preventing tick attachment and killing existing ticks within 24–48 hours.
When do flea and tick drops start to work? - in detail
Spot‑on products for dogs and cats begin to spread across the skin within minutes after application. The active ingredients dissolve in the oily layer of the skin and travel through the bloodstream to reach the surface of the skin and hair follicles, where they affect parasites that bite or crawl onto the animal.
Typical onset of activity
- Fleas: Adult fleas start to die within 4–6 hours. Most formulations achieve 90 % mortality by the end of the first 24 hours. Egg production is suppressed almost immediately because adult fleas are eliminated before they can lay eggs.
- Ticks: Ticks attached to the animal are killed within 24–48 hours, depending on the compound and the tick species. Unattached ticks in the environment are not affected; control relies on preventing attachment.
Factors influencing speed of action
- Body weight and coat thickness: Larger animals or those with dense coats may require a few extra minutes for the medication to reach the skin surface.
- Temperature: Warmer skin temperatures accelerate absorption, shortening the time to effect.
- Product formulation: Products containing imidacloprid, fipronil, or selamectin typically act faster than those based solely on pyrethrins.
- Application site: Applying the drop directly to the skin, not just the hair, ensures quicker distribution.
What to expect after the first dose
- Within the first hour, the medication spreads over the skin surface.
- By the sixth hour, most adult fleas present on the animal are dead.
- After 24 hours, the majority of attached ticks are eliminated.
- Continuous protection is maintained for the labeled duration (usually 30 days), provided the product is reapplied on schedule.
If fleas or ticks are observed after the expected killing window, verify correct dosing, ensure the product was applied to a clean, dry spot, and consider environmental treatment to reduce reinfestation.