How do flea drops act? - briefly
Flea drops deliver systemic insecticides that penetrate the animal’s skin, enter the bloodstream, and reach fleas feeding on the host. The compounds interfere with the parasites’ nervous system, causing swift paralysis and death.
How do flea drops act? - in detail
Flea spot‑on products are applied to a thin area of skin, usually between the shoulder blades. The formulation contains an insecticidal or insect growth‑regulating active ingredient that penetrates the stratum corneum within minutes. Once absorbed, the compound spreads across the lipid layer of the skin and into the sebaceous glands, creating a reservoir that releases the agent onto the fur and into the surrounding environment.
The active ingredient reaches fleas through three primary pathways:
- Contact toxicity – When a flea walks on the treated coat, the compound interferes with the insect’s nervous system. Molecules such as fipronil or imidacloprid bind to GABA‑gated chloride channels, causing uncontrolled neuronal firing and rapid paralysis.
- Systemic action – Ingredients like selamectin or fluralaner are absorbed into the bloodstream. Feeding fleas ingest the drug, which disrupts neurotransmission by blocking ligand‑gated chloride channels, leading to death within hours.
- Growth inhibition – Certain formulations include insect growth regulators (IGRs) such as pyriproxyfen. These agents mimic juvenile hormone, preventing eggs and larvae from developing into mature fleas, thereby breaking the life cycle.
Pharmacokinetic properties ensure prolonged protection. After the initial distribution, the drug remains active in the oil layer of the skin for weeks, resisting wash‑off from bathing or rain. Concentrations gradually decline, but therapeutic levels persist long enough to kill newly encountered fleas and suppress emerging populations.
Dosage is calibrated to the animal’s weight. Over‑application can increase systemic exposure without enhancing efficacy, while under‑dosing may allow survivors to develop resistance. Manufacturers set a minimum interval—typically 30 days—for re‑application to maintain consistent plasma and coat concentrations.
Safety relies on selective toxicity: the molecular targets are present in arthropods but absent or significantly different in mammals. Toxicity studies confirm low risk when used as directed, though accidental ingestion or application to damaged skin can cause adverse reactions.
In practice, the mechanism combines immediate kill of adult fleas, interruption of reproductive development, and sustained distribution across the host’s exterior, delivering comprehensive control over the ectoparasite population.