How do flea drops applied to a cat's neck work? - briefly
The liquid is applied to the skin at the back of the neck, where it mixes with the cat’s oils and spreads across the body, entering the bloodstream to reach developing fleas and kill them before they emerge. Once in the circulatory system, any flea that bites the animal contacts a lethal dose of the insecticide, effectively preventing infestation.
How do flea drops applied to a cat's neck work? - in detail
Spot‑on flea treatments for cats are liquid formulations applied to a small area of skin at the base of the skull. The product contains an active ingredient such as a neonicotinoid (e.g., imidacloprid) or an insect growth regulator (e.g., pyriproxyfen). When the solution contacts the hair and skin, it spreads across the surface through capillary action and is absorbed through the epidermis into the systemic circulation.
Absorption occurs within minutes; the drug enters the bloodstream and is carried to the skin surface throughout the body. Fleas that bite the cat ingest the compound while feeding on blood, or they come into direct contact with the chemical on the cat’s fur. Because the active molecule is present in the lipid layer of the skin, it remains effective for several weeks.
Neonicotinoids bind to nicotinic acetylcholine receptors in the flea’s nervous system, causing paralysis and death within hours. Insect growth regulators interfere with chitin synthesis, preventing larvae from developing into viable adults. The dual action eliminates existing adult fleas and suppresses the emergence of new generations.
Efficacy lasts typically 30 days, matching the recommended re‑application interval. Dosage is weight‑based; manufacturers provide charts to select the correct volume for cats of different mass. The product is designed for topical use only; ingestion can cause toxicity, so accidental swallowing must be avoided. Skin irritation is rare but possible in animals with pre‑existing dermatological conditions.
Proper application involves parting the hair, applying the entire dose to the skin without touching the cat’s fur, and allowing it to dry before the cat resumes normal activity. Avoid bathing or swimming for at least 24 hours after treatment, as water can reduce absorption. Regular monitoring for signs of resistance—reduced flea kill rates or persistent infestations—helps maintain control, prompting a switch to an alternative class if necessary.