Fleas on dogs: how to spot them and get rid of them

Reading time 6 min · Level 1: Why the symptom happens

The short answer: Fleas on a dog usually show up as itching over the lower back, the base of the tail and the back of the thighs. You may also see small black specks in the coat that turn reddish brown on wet paper. In Sweden these are mostly fleas from birds, hedgehogs or rodents that the dog has picked up outdoors. They cannot breed on a dog and often disappear on their own. The cat flea is the one that causes real trouble, because it breeds indoors. Then every animal in the household needs treating with a product from the pharmacy or vet while the home is cleaned. So the first thing to find out is which flea it is.

How to tell if your dog has fleas

Fleas are small, brown, flat insects, around one to six millimetres long depending on the species¹. They move fast in the coat and can jump up to 30 centimetres⁴. Often you will not see the fleas themselves but their droppings.

Try this: stand your dog on white paper or a pale towel and go through the coat with a fine flea comb, especially along the back and at the base of the tail. Flea dirt looks like small, dark, slightly curved specks. If you moisten them on the paper they take on a reddish brown tint from the blood the flea has sucked¹. Ordinary dirt does not.

The itch tends to sit where fleas like to be. SVA, the Swedish National Veterinary Institute, describes dandruff and hair loss mainly over the lower back¹. AniCura mentions rashes and hair loss on the back, hindquarters, flanks, tail and around the anus². If you get small itchy bites on your arms and legs, that is another clue¹. But not every dog shows symptoms, so a dog that is not scratching can still carry fleas into the house¹.

Which flea it is decides everything

1. Fleas from birds, hedgehogs and rodents. These are what is most often found on Swedish dogs and cats¹. The dog has sniffed a bird's nest, a hedgehog's bed or a vole tunnel. The fleas bite and can cause short-lived discomfort, but they need blood from their own host to breed. Combing them out is often enough¹. If the dog is bothered, the vet may still recommend a product that removes the adult fleas².

2. The cat flea. Despite the name it attacks dogs just as readily as cats, while the dog's own flea is uncommon. The cat flea is a common problem in southern Sweden² and thrives in our indoor environment³. This is the one that can drag on.

The difference can only be seen under a microscope, in the shape of the head and the small combs on the head and front of the body². So catch a few fleas on a piece of tape or in a glass when you comb³. Your vet can send them off for identification. FirstVet also sells a test kit analysed by SVA⁴.

Why the cat flea is so hard to get rid of

A female cat flea lives two to three weeks and usually lays 15 to 20 eggs a day². The eggs drop off the dog into the sofa, the rug and the dog bed. They hatch after one to two days, sometimes up to two weeks depending on temperature. The larva spins a cocoon, and under favourable conditions the pupa can survive in the surroundings for around a year. The adult flea hatches when it senses warmth, vibration or carbon dioxide, in other words when an animal or a person walks past¹.

That means two things. The number of eggs, larvae and pupae in the home is far larger than the number of fleas on the dog². And new fleas keep hatching for weeks after you have treated the dog. Treating only the dog, once, is rarely enough.

What fleas can lead to

Flea allergy. Flea saliva contains substances that irritate the skin and can cause allergy. Worldwide, flea allergy is one of the most common causes of itching and skin problems in dogs². An allergic dog scratches far more than the number of fleas would explain, sometimes with hair loss and marked skin irritation⁴.

Skin infections. Skin that has been scratched raw can develop bacterial infections on top of the bites¹.

Tapeworm. Fleas can carry tapeworm, which the dog swallows while grooming⁴. Tell your vet if your dog has had fleas so you can decide together on worming.

Anaemia. Heavy infestations can cause anaemia¹. It is uncommon and mainly affects small dogs and dogs that are already weakened⁴.

When to see a vet

The same day if a small dog, or a dog that is already weakened, has a lot of fleas and also seems more tired than usual. That can be a sign of anaemia⁴.

Within a few days if your dog has itching, hair loss, sores or red skin⁴. The vet can identify the fleas, rule out other causes of the itch and choose a product to suit your dog's weight, age and the other animals you have. Many substances are registered for this in Sweden¹. The Swedish Medical Products Agency publishes a treatment recommendation for parasites in dogs and cats that vets work from⁵. The same applies if the itching continues after the fleas seem to be gone.

What you can do yourself

Comb first, buy second. Confirm that it is fleas and keep a few for identification.

Treat all animals at the same time. If you have more dogs or cats, all of them should be treated at once, otherwise the fleas simply move between them³. There are non-prescription products at the pharmacy and prescription products your vet can provide³. For cat fleas, a product that stops new eggs from hatching is often used, and AniCura describes a tablet given every month for six months².

Be careful with cats. Permethrin, found in some flea products for dogs, is toxic to cats and must not be used on them¹.

Clean the home. Vacuum sofas, rugs, floor gaps and the dog's sleeping places often, and throw away the vacuum bag afterwards. Wash the dog's blankets and beds. All stages are also killed by freezing¹. With a large infestation you may need a pest control company³.

Check your tick product. Many tick products also work against fleas, which is probably one reason fleas have become less common³. Ask at the pharmacy what the product you already use covers, and how often your dog can be washed while using it.

Frequently asked questions

Can fleas from my dog bite people?

Yes. Fleas can suck blood from people and cause small itchy rashes¹.

Can my dog have fleas even if I cannot see any?

It is possible. A flea-allergic dog can scratch intensely from just a few bites. Look for flea dirt with a comb and wet paper. If you find nothing but the itching continues, it may be something else, and your vet should examine the dog.

How long does it take to get rid of cat fleas?

Think in months, not days. New fleas hatch from pupae in the home for a long time after the dog has been treated, which is why treatment often runs for several months.

Do fleas disappear in winter?

Not the cat flea. It thrives indoors all year round, and the pupa can also wait in the surroundings for a long time before hatching¹.

That was the short answer. If you have a question about your own pet, email us at info@herbiovet.se. We reply within one working day.