Fleas on Dogs

Fleas on dogs cause scratching around the tail, belly and thighs and leave black flea dirt in the coat; nearly all of them are cat fleas picked up from yards, other pets and wildlife. The fastest fix is an oral flea tablet that starts killing within about 30 minutes, but the dog stays flea-free only if it keeps getting a long-acting preventive and the house is treated at the same time.

What do fleas look like on dogs?

Adult fleas are 1/16 to 1/8 inch, reddish-brown to black, shiny and narrow, and they run fast through fur or jump off. On dark or thick coats you may only see them on the belly, where hair is thin. Check:

• the base of the tail and rump,
• the belly and groin,
• inner thighs, armpits and neck.

Run a fine-toothed flea comb through the coat over white paper. Live fleas get trapped in the teeth; black specks that smear red when wet are flea dirt. More photos: what do fleas look like.

Signs of fleas on dogs

• Scratching, chewing or licking, especially over the lower back and tail base.
• Small red bumps, scabs, hot spots.
• Hair loss and thickened skin on the rump: classic flea allergy dermatitis. One bite a day is enough to keep an allergic dog itching.
• Tapeworm segments like rice grains near the tail or in bedding.
• Pale gums and lethargy in puppies or small dogs with heavy infestations. See a vet.
• Bites on people's ankles.

How do dogs get fleas?

• Yards that raccoons, opossums, feral cats or foxes cross. Flea larvae develop in shady, moist spots, and new adults jump on as your dog walks by.
• Other animals: dog parks, daycare, boarding, groomers, a visiting dog, and especially the household cat.
• The house itself. Cocoons in carpet can wait months. Moving into a home where pets lived is a common trigger.
• Wildlife under the house in a crawl space or under a porch.

What kills fleas on dogs instantly

• Nitenpyram tablets: start killing adult fleas within about 30 minutes; effect lasts about 24 hours. No prescription needed. This is also the answer to "what kills fleas on dogs instantly without bathing."
• Dish soap bath: a ring of lather around the neck first, then the body, leave 5-10 minutes, rinse and comb. Kills fleas on the dog now, nothing after. Details in home remedies for fleas.
• Flea comb: removes fleas immediately, safe for puppies and pregnant dogs.

How to get rid of fleas on a dog: lasting control

Your vet will pick the product based on age, weight, health and lifestyle. Main US options:

• Oral isoxazolines (afoxolaner, fluralaner, sarolaner, lotilaner): monthly or 12-week chews, kill fleas within hours and usually cover ticks too. Prescription. The FDA has noted rare neurological reactions such as tremors or seizures, so tell your vet about any seizure history.
• Spinosad chews: monthly, fast-acting flea kill.
• Spot-ons: fipronil with S-methoprene, imidacloprid (often with permethrin or other actives). Many are over the counter. Products containing permethrin are for dogs only; keep cats away from a treated dog.
• Collars: a few vet-recommended collars give months of protection; most cheap ones don't.

Keep at it monthly for at least three months to break the cycle, and year-round in warm states. Weigh the dog and buy the right size: an under-dosed product invites failure, an overdose risks side effects.

Treat the house and the yard

Treating only the dog leaves 95% of the population behind.

1. Wash the dog's bed, blankets and any couch throws in hot water; dry on high. Repeat weekly.
2. Vacuum every day for two to three weeks: carpets, under furniture, along baseboards, car seats if the dog rides.
3. Spray carpets and furniture undersides with a product combining an adulticide and an IGR; repeat in 10-14 days.
4. Treat shady outdoor spots the dog rests in: under the deck, the dog house, along fences.
5. Treat every other pet, especially cats, with cat-safe products.

Full plan: how to get rid of fleas in the house.

What fails

• Bathing every few days instead of using a preventive.
• Treating the dog but not the cat.
• Stopping after the first month because fleas "disappeared."
• Garlic, brewer's yeast, vinegar rinses and essential-oil collars. They don't kill fleas, and garlic is toxic to dogs.

When to see the vet

• Puppies with fleas, or any dog with pale gums or weakness.
• Raw, oozing skin, hair loss, or itching that doesn't settle after two to three weeks of good flea control.
• Tapeworm segments.
• Any reaction after a flea product: bathe off spot-ons with dish soap and call your vet or a pet poison hotline.