Fleas and ticks: what actually works
By the time you see fleas on the pet, the great majority of the problem is in your carpet.
The 5% rule
Adult fleas on your pet represent roughly 5% of an infestation. The other 95% — eggs, larvae and pupae — is in carpets, bedding, sofas and floorboards. Treating only the animal is why infestations come back three weeks later.
Dealing with an infestation properly
- Treat every pet in the house on the same day, including ones that seem unaffected and indoor-only cats.
- Wash all bedding at 60°C — pet beds, your bedding, blankets, throws.
- Vacuum daily for two weeks, including edges, under furniture and sofa cushions. Vibration triggers pupae to hatch, which is useful — it brings them out where treatment can reach.
- Empty the vacuum outside each time.
- Treat the environment with a household spray containing an insect growth regulator if the infestation is established.
- Expect three months to fully clear, because pupae can lie dormant.
Never use dog flea products on cats
Permethrin, present in some dog spot-ons, is highly toxic to cats and causes seizures and death. This includes a cat grooming a recently treated dog. Read every label, and keep treated dogs separate until dry.
Ticks
Ticks carry Lyme disease and other infections. Transmission generally takes some hours of attachment, so prompt removal matters more than anything else.
Use a tick hook or fine-tipped tweezers. Grip as close to the skin as possible and twist or pull straight out with steady pressure. Do not burn it, smother it in petroleum jelly, or squeeze the body — all of these can cause the tick to regurgitate into the wound, which is exactly what you are trying to avoid. Clean the area afterwards and note the date.
Check after every walk in long grass, woodland or moorland, paying attention to ears, neck, armpits, groin and between toes.
Prevention beats reaction
Year-round prevention is now generally recommended, because centrally heated homes let fleas breed through winter. Prescription products from a vet are usually more effective than supermarket ones, and are dosed by weight — an important reason to know your pet's current weight rather than guessing.
Garlic, essential oils, ultrasonic collars and brewer's yeast have no good evidence behind them, and some essential oils are toxic to cats.
The flea life cycle, and why timing feels random
| Stage | Where | How long |
|---|---|---|
| Egg | Falls off the pet into carpet and bedding | 2–10 days |
| Larva | Deep in carpet fibres, avoiding light | 1–2 weeks |
| Pupa | Sealed cocoon, resistant to insecticide | Days to many months |
| Adult | On the pet | Weeks |
The pupa stage is why infestations appear to come back from nowhere. Cocoons wait for vibration, warmth and carbon dioxide before hatching — which is exactly what happens when a family returns from holiday to a house that has been quiet for two weeks. Nothing failed; the pupae were simply waiting.
It is also why vacuuming is genuinely part of treatment rather than just cleaning. The vibration triggers hatching, bringing fleas out of the one stage that treatment cannot reach.
Diseases these parasites actually carry
- Tapeworm — swallowed when a pet grooms and ingests a flea. Rice-like segments around the tail are the usual sign, and any flea infestation should be followed by worming
- Flea allergic dermatitis — an allergy to flea saliva. A single bite can cause weeks of intense itching, which is why "I only saw one flea" does not mean the itching is unrelated
- Anaemia — a heavy burden on a puppy, kitten or small elderly pet can cause dangerous blood loss
- Lyme disease — tick-borne, causing lameness, fever and joint swelling, sometimes weeks after the bite
- Babesiosis and ehrlichiosis — tick-borne, increasingly seen as tick ranges expand
- Lungworm — not a flea, but relevant: spread by slugs and snails, potentially fatal, and only prevented by specific wormers
Choosing a product
| Type | Notes |
|---|---|
| Spot-on | Applied to skin at the neck. Keep pets separated until dry, and do not bathe for 48 hours either side |
| Oral tablets / chews | Not affected by swimming or bathing. Often faster-acting. Some cover ticks too |
| Collars | Long duration. Use a breakaway design for cats |
| Shampoos | Kill fleas present at that moment with no lasting protection. Not a treatment on their own |
| Household sprays | Target eggs and larvae. Look for an insect growth regulator |
Dosing is by weight, and an under-dosed pet is an untreated pet. This is a practical reason to know your pet's current weight rather than the weight they were two years ago.
Prevention schedule
Year-round treatment is now the usual recommendation in centrally heated countries, because fleas breed indoors through winter regardless of the weather outside. Set a monthly phone reminder — lapses of a few weeks are how most infestations start, and by the time you notice, the environmental stage is already established.
Treat every pet in the household on the same day, including indoor-only cats. Fleas arrive on trouser legs and in carrier bags, and an untreated indoor cat becomes the reservoir that reinfests everyone else.
What does not work
Garlic, brewer's yeast, ultrasonic collars, and most essential oil preparations have no reliable evidence behind them. Tea tree and several other essential oils are actively toxic to cats, and some "natural" flea products marketed for dogs have caused serious harm to cats in the same household.
Treating the home matters as much as treating the pet — most of a flea population is eggs, larvae and pupae in carpets, bedding and floor cracks rather than adults on the animal. Vacuum daily during an infestation and wash bedding at 60°C. Parasite risk in warm weather →
Common questions
Why do fleas keep coming back after treatment?
Because adult fleas on the pet are only about 5% of the population. Eggs, larvae and pupae in carpets and bedding hatch over the following weeks. Clearing an infestation takes environmental treatment and up to three months.
How do I remove a tick safely?
Use a tick hook or fine-tipped tweezers, grip close to the skin, and pull or twist straight out with steady pressure. Do not burn it or cover it in anything — that can make the tick regurgitate into the wound.
Can I use dog flea treatment on my cat?
No. Some dog products contain permethrin, which is highly toxic to cats and can be fatal, including from grooming a recently treated dog.
How long does it take to get rid of fleas?
Usually up to three months. Pupae can lie dormant in cocoons for months and are resistant to insecticide, so they continue hatching after the pets have been treated. Daily vacuuming helps by triggering them to emerge.
Do indoor cats need flea treatment?
Yes. Fleas are carried indoors on clothing and bags, and an untreated indoor cat becomes a reservoir that reinfests the rest of the household.
Can fleas cause worms?
Yes. Tapeworm is transmitted when a pet swallows an infected flea while grooming, so any flea infestation should be followed by a worming treatment.