Fleas Came Back After Treatment? Blame the Cocoons

Why fleas came back after treatment, right at week two

Here's the short version of the flea life cycle. Our cat flea page has the longer one.

An adult flea on your dog or cat lays eggs, and the eggs fall off wherever the animal sleeps, walks or stops to scratch. They hatch into tiny larvae that hate light. The larvae crawl deep into carpet fibers, along baseboards, into pet beds and into damp, shaded soil outside, and they live on the dried droppings adult fleas leave behind (the black specks people call flea dirt). Then each larva spins a sticky cocoon and turns into an adult inside it.

That adult doesn't have to leave right away. It can sit in the cocoon and wait for a sign that a meal is close: footsteps, vibration, body heat, the carbon dioxide we breathe out. When it senses one, it pops out and jumps on the nearest warm body.

Now picture the house on treatment day. There are adults on the pet, eggs and larvae in the carpet, and a hidden layer of cocoons. Treatment knocks back the adults and the larvae it reaches. The cocoons stay put. Over the next couple of weeks they keep opening, and every flea that comes out looks like a new problem, even though it's been in your house the whole time.

Fleas keep coming back? Look at these first

When fleas hang on past the normal hatch, it's usually one of these:

• One pet was skipped. The cat that "never goes outside" can keep the cycle going for the dog. Ask your vet about every animal in the house.
• The pet's flea care lapsed. A late dose or a missed month gives a fresh batch of eggs a head start. Your vet can tell you what fits your pet and how often.
• The yard wasn't part of the plan. If the dog lies under the same shady tree every afternoon, fleas waiting in that soil hop right back on.
• Wild animals are visiting. Raccoons, opossums and stray cats carry fleas and drop eggs where they bed down, often under decks, sheds and thick hedges.
• The vacuuming slowed down. Everyone vacuums daily the first few days. By week two it slips, and that's often right when cocoons are opening.

What we treat: the home and the yard, together

Fleas live in two places around a South Florida home, so we treat both on the same visit.

Inside, a technician treats the spots where flea eggs and larvae collect: carpets and rugs, along baseboards, under and around furniture, and the places your pets rest. Before we come, pick up toys, shoes and anything on the floor, and vacuum so the treatment reaches the carpet fibers.

Outside, fleas in a yard in Florida don't sit out in full sun. They stay where it's shady, damp and sheltered: under the deck or raised porch, along the fence line the dog patrols, beneath shrubs, beside the AC pad, in the dog run, under the patio chair where the cat naps. Our flea yard treatment goes to those resting areas around the home instead of blanketing open grass. We don't take care of grass or plants, so this is about the fleas, nothing else. The technician will ask where your pets spend their time and start there.

Keep kids and pets off treated areas until dry, and follow your technician's instructions.

When the house, the yard and the pet are all handled in the same window, the cycle has far fewer places to restart. See our flea and tick control page for how a visit works.

Flea FAQs