How does a flea treatment for cats work on the scruff? - briefly
The medication applied to the nape of the neck spreads across the skin and into the bloodstream, killing fleas that bite the cat. This systemic action also prevents newly emerging fleas from surviving on the animal.
How does a flea treatment for cats work on the scruff? - in detail
Topical flea products for felines are applied to the skin at the nape of the neck, a region where the cat cannot easily lick the spot. The formulation—usually a liquid or gel—contains an insecticidal active ingredient such as fipronil, imidacloprid, selamectin, or fluralaner. When the solution contacts the fur, it spreads across the skin surface and penetrates the outer epidermal layers within minutes.
Absorption occurs through the stratum corneum. The drug enters the dermal capillary network and is carried by the bloodstream to the entire body. Distribution follows the cat’s circulatory system, delivering the compound to the skin, hair follicles, and sebaceous glands where adult fleas, larvae, and eggs reside. Because the medication circulates systemically, fleas feeding on any part of the animal are exposed to a lethal dose.
The pharmacodynamics of each active ingredient differ:
- Fipronil disrupts the insect’s GABA-gated chloride channels, causing uncontrolled nerve firing and death.
- Imidacloprid binds to nicotinic acetylcholine receptors, producing paralysis.
- Selamectin interferes with glutamate‑gated chloride channels, leading to paralysis of parasites.
- Fluralaner blocks GABA and glutamate receptors, providing rapid kill and long‑lasting protection.
The dosage is calibrated to the cat’s weight, ensuring a concentration that kills fleas while remaining safe for the host. After application, the product forms a thin protective film that resists washing and persists for weeks, depending on the compound’s half‑life. This film continuously releases the active ingredient, maintaining lethal levels in the cat’s blood and on its skin.
Safety mechanisms include low systemic toxicity, rapid metabolism, and limited absorption through intact skin. The nape is chosen because it has reduced grooming access, allowing the medication to remain in place long enough to achieve full systemic distribution before any potential removal by licking.
In summary, applying a flea control solution to the scruff creates a localized reservoir that quickly penetrates the skin, enters the circulatory system, and distributes a neurotoxic agent throughout the animal. The agent kills fleas on contact and prevents reinfestation by maintaining effective concentrations in the cat’s tissues for an extended period.