Fleas are not just an itch. A single female lays fifty eggs a day, most of them on your carpet and bedding rather than the cat. By the time you see fleas on the cat, you have a household problem that takes three months to resolve. Ticks carry diseases, some of them serious. Both are preventable for the cost of a coffee a month.
Indoor cats need prevention too. Fleas come in on shoes, on dogs, on visiting humans, and on the family cat that briefly escaped. Mosquitoes carry heartworm, also preventable with most modern products, and they get in through any open window. I had a strictly indoor cat get fleas during a heatwave in 2023. Brought in on a delivery box, I think. Took six weeks and three vacuum bags to clear.
The three main options
Spot-on (topical)
A liquid you apply to the skin between the shoulder blades, once a month. The cat can't lick it off there, and it spreads through the skin's oil layer to cover the whole body within a day.
- Pros: widely available, broad coverage (most also handle ear mites, some handle worms), works within hours.
- Cons: the cat is slightly damp and smells of the product for a day. Don't pet the spot or let other animals lick it.
- Examples: Revolution Plus, Advantage II, Frontline Plus, Bravecto topical.
This is the default for most cats.
Oral tablets or chews
Newer and getting more popular. The cat eats it. The active ingredient circulates in the blood. Fleas die when they bite.
- Pros: no residue on the coat, no application issues, works fast.
- Cons: harder to dose if your cat won't take pills. Fewer cat-specific options than for dogs.
- Examples: Comfortis (flea only), Credelio (flea and tick).
Worth asking the vet about if your cat hates spot-ons.
Collars
A plastic collar that releases active ingredient slowly over six to eight months.
- Pros: very long-lasting, low maintenance, good for cats that won't tolerate monthly application.
- Cons: quality varies wildly. The cheap supermarket ones are useless and some contain organophosphates that are dangerous to cats. Only Seresto has solid evidence and broad veterinary use.
- Caveat: must be a quick-release breakaway design, or your cat can hang itself by the collar on a branch or fence.
Useful as a backup, not the strongest single option.
What to avoid
- Permethrin. Fatal to cats even in small amounts. It's the active ingredient in many dog flea products. Never use a dog product on a cat, and keep recently-treated dogs separate from cats for 24 hours.
- Essential oil products marketed as "natural." Tea tree, pennyroyal, and several others are toxic to cats. Most don't work even when they don't poison the cat.
- Garlic, brewer's yeast, ultrasonic devices. No evidence any of these do anything.
- Flea shampoos as a prevention strategy. They kill what's on the cat at that moment and do nothing about the environment. Treat the underlying infestation and use a proper monthly preventative going forward.
Signs of an infestation
- Excessive scratching, especially at the neck and base of the tail.
- Flea dirt. Tiny black specks in the coat that turn red on a wet paper towel. That's digested blood.
- Small scabs along the spine. Many cats are allergic to flea saliva and react to a single bite.
- Live fleas. Run a fine-toothed flea comb through the coat, especially around the neck and belly. You'll see them.
- Pale gums and lethargy in a kitten or small cat. Fleas can cause anemia.
If you find fleas
- Treat the cat with a fast-acting product (Capstar kills within hours).
- Start monthly preventative the same day.
- Treat the house. Wash all bedding the cat uses on hot. Vacuum carpets, sofas, and along the edges of every room, and throw out the bag or empty the canister into an outdoor bin. A residual spray helps in heavy infestations.
- Treat every pet in the household, even the ones that look fine.
- Keep going for three months. Eggs in the carpet hatch on their own schedule. One round of treatment is not enough. Most reinfestations are people stopping at week six.
The whole problem is much smaller if you never let it start. Pick a product, set a monthly reminder, and stick to it.