How does flea shampoo act on fleas? - briefly
Flea shampoo delivers insecticidal agents (e.g., pyrethrins, insect growth regulators) that penetrate the flea’s cuticle, disrupt neural function, and cause swift mortality. The treated coat remains coated, killing any fleas that contact it and reducing the chance of re‑infestation.
How does flea shampoo act on fleas? - in detail
Flea shampoo is a liquid preparation applied directly to an animal’s fur, delivering insecticidal compounds that contact and penetrate adult fleas. The formulation typically combines a neurotoxic agent with surfactants and solvents that facilitate skin penetration and flea exposure.
Common active ingredients include:
- Pyrethrins or synthetic pyrethroids (e.g., permethrin, cypermethrin) – bind to voltage‑gated sodium channels in the flea nervous system, prolonging channel opening and causing uncontrolled nerve firing.
- Imidacloprid – acts as a nicotinic acetylcholine receptor agonist, leading to paralysis and death.
- Fipronil – blocks GABA‑gated chloride channels, disrupting inhibitory neurotransmission.
- Insect growth regulators such as methoprene – interfere with embryogenesis, preventing egg hatch and larval development.
The neurotoxic agents work on contact; when a flea walks through the lather, the chemicals infiltrate the exoskeleton, reach the nervous tissue, and induce rapid paralysis. This effect occurs within minutes, eliminating feeding and movement.
Surfactants and soaps in the shampoo lower surface tension, allowing the solution to spread evenly across the coat and coat the flea’s cuticle. The resulting wet environment disrupts the flea’s respiratory spiracles, contributing to suffocation. Additionally, the detergent action loosens debris and flea feces, removing eggs and larvae that might otherwise re‑infest the host.
After rinsing, a residual layer of active ingredient remains on the skin and hair, providing continued protection for several hours. This residual activity reduces the likelihood of new fleas establishing a feeding site, and the presence of an insect growth regulator suppresses the development of any eggs that may have been transferred to the environment during grooming.
Safety considerations include:
- Limited systemic absorption; most active compounds stay on the surface, minimizing toxicity to the host.
- Species‑specific contraindications: pyrethroids are toxic to cats due to deficient hepatic metabolism.
- Recommended concentration and contact time must be observed to avoid skin irritation.
Repeated exposure can select for resistant flea populations. Rotating products with different modes of action, such as alternating a pyrethroid‑based shampoo with one containing an insect growth regulator, mitigates resistance development.