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Why Do Fleas Come Back After Treatment?

Written by PestMan Editorial TeamTechnical review pendingPublished Updated

Quick answer

Fleas often seem to come back because treatments do not kill pupae protected inside their cocoons. New adults keep emerging for several weeks after treatment. Untreated pets, wildlife under the house, and not vacuuming enough can also keep the cycle going. Continuing pet treatment and daily vacuuming for a few weeks usually breaks the cycle.

Why this happens

Most of a flea population is in carpets and bedding as eggs, larvae and pupae. Pupae are the most resistant stage.

Vacuuming stimulates pupae to hatch, exposing new adults to treated surfaces and to pet treatments.

If even one pet is untreated, it can keep feeding and reintroducing fleas.

What you can do

  • Treat all pets at the same time with vet-recommended products and continue monthly.
  • Vacuum daily for at least two to three weeks after treatment.
  • Wash pet bedding weekly on hot.
  • Check cars, pet carriers and outdoor resting areas.

When professional help may be needed

If fleas persist for more than four to six weeks after treatment and pets are protected, a follow-up inspection can check for wildlife sources or untreated areas.

Fleas

Tiny, wingless, jumping insects that feed on the blood of pets and people. Most of a flea population lives in carpets, bedding and yards as eggs, larvae and pupae, not on the pet.

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Sources & further reading

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