Fleas and their Symptoms

In this lesson, we’ll cover what fleas are, as well as the symptoms you can expect to see when a cat or dog has fleas.

What are fleas?

fleas in pets

Fleas are not just any pests; they are tiny insect ‘ectoparasites’ (like ‘external’, as they live on the outside of the animal, and ‘parasites’ because they feed from an animal to that animal’s detriment).

Despite being small, they have the ability to make the lives of our beloved pets truly miserable. These tiny creatures primarily target pets, making dogs and cats their preferred hosts, although they won’t shy away from occasionally making a meal out of humans.

How did my pet get fleas?

The journey of a flea onto your pet can begin in a multitude of ways. Most flea infestations are picked up by contact with other animals – the fleas jump off them, and onto your pet. But they can live for a while in the environment, so your pet could get them from visiting places where other pets have been.

Photo of two dogs on a walk

Common ways that pets get fleas include:

  • Contact with other animals
  • Picking up live fleas that have recently jumped off a pet onto the pavement or grass, even if no physical contact between pets (this includes at the park, on walks, and indoors at the grooming salon, pet shop, or vet practice)
  • Entering a home or environment where fleas are dormant (note: fleas have to have entered the home within the last 12 weeks to be dormant there, but there do not need to be living pets or an active infestation – fleas can hide for up to 12 weeks and hatch from cocoons when they sense a pet nearby)
  • Fleas brought into the house on your clothes or on other inanimate objects (‘hitchhikers’) – even indoor-only pets can get fleas!

Is it fleas?

While fleas may not have wings, they are adept jumpers, allowing them to leap onto pets effortlessly. Once on board, they puncture the skin to feed on the pet’s blood. The aftermath of a flea bite is far from pleasant. The immediate reaction includes irritation and an unrelenting itch.

For some pets, this isn’t the end of their ordeal. They may develop flea allergy dermatitis (FAD), a condition stemming from an allergic reaction to flea saliva, leading to heightened skin sensitivity. These pets are over-sensitive to every flea bite, leading to extreme itchiness.

Use the accordion below to read common signs of fleas in pets and confirm whether the signs you’re seeing are due to fleas

Signs your dog has fleas

  • Scratching and skin biting, particularly around the tail and lower back.
  • Visible fleas, often in hairless areas like tummy and armpits
  • Patches of hair loss or broken hairs from so much scratching
  • Spotting “flea dirt” which looks similar to black pepper, but is essentially flea poo. You can differentiate this from dried mud by combing it onto a wet piece of kitchen towel and watching for red-brown rings to develop around the poo as it dissolves.
  • Appearance of hot spots due to constant scratching.
  • In severe infestations, dogs can even develop anaemia, which shows as pale gums.

Signs your dog has flea allergy (FAD)

Dogs exhibiting FAD typically display intense itching and the following symptoms:

  • Reddened skin, accompanied by pimples and areas that might ooze or crust over.
  • A greasy-feeling coat coupled with dandruff.
  • Areas where the fur is thin or completely absent.
  • Skin that becomes thicker and takes on a darker hue.

The most noticeable regions for these signs include the base of the tail, the lower back, inner thighs, the lower abdomen, and the sides. The base of their ears and the underside of the throat may also show these symptoms.

Signs your cat has fleas

Cats are often the culprits when it comes to bringing in an infestation, as they don’t always show signs of having fleas. Here are some things you might spot

  • Cats may frequently groom or lick themselves.
  • Skin might have sore areas.
  • Bald patches or areas of short hair where they’ve overgroomed, especially at the tail base and lower back.
  • Cats may seem more restless or agitated – sometimes their fur ‘twitches’
  • Seeing adult fleas moving in the fur, especially in thinly-haired areas like armpits or belly
  • Cats might roll or writhe, trying to relieve itching sensations

Signs your cat has flea allergy (FAD)

Flea-allergic dermatitis (FAD) is a reaction to flea saliva in cats. When bitten by a flea, cats with FAD undergo severe itching and display a distinct rash. This rash often feels gritty under the fur and usually appears on their head, neck, belly, and back legs. Cats coping with FAD may:

  • Excessively scratch, lick, and bite their skin.
  • Develop red, sore, infected areas on their body.
  • In extreme cases, suffer from a condition named ‘eosinophilic dermatitis’.

Flea allergic dermatitis needs treatment by a veterinarian as these cats often have secondary skin infections and their itch needs medication. Moving forward, it will be essential to ensure these cats don’t get fleas in future – the rest of the course will be helpful there!

Signs of fleas in the house

If your pets have fleas, and they’ve been indoors, you can guarantee that there are fleas in your house. But if your pets don’t show many signs of fleas, you might spot signs of fleas in your house before you spot them on your pets. These signs include:

  • Finding flea dirt on pet bedding or furniture.
  • Observing fleas actively jumping on carpets or furniture.
  • Human family members might get bitten, mostly around ankles or legs.

Flea bites on humans

Fleas prefer pets to humans, but if there’s a bad infestation or pets are in short supply, they can bite humans.

  • Appearance of small, red, and itchy raised spots.
  • Bites often group in clusters or line patterns.
  • Common areas of bites include ankles, waist, armpits, or the bends of elbows and knees.
  • Scratching these bites excessively can lead to secondary infections.

Are fleas a problem?

Other than their annoying itch (especially if you’re unlucky enough to have an allergy!), fleas can also carry diseases into your home. These include:

  • Bartonellosis or ‘cat scratch disease’, a bacterial disease that can cause headaches and fever in humans
  • Tapeworm, which is carried by fleas
  • Feline infections anaemia (caused by small bacteria called Mycoplasmas)


Fleas are small insects that jump onto our pets and feed on their blood. It’s fairly rare to spot an actual flea, since they don’t spend much time out in the open. More commonly, you’ll see flea dirt (aka flea poo) and itching or grooming as the first signs of a problem. Some pets are allergic to fleas, and only need to be bitten by one flea to have an extreme reaction – we call this ‘flea allergic dermatitis’.

Key Takeaway

Fleas are not the only cause of itching in pets, but they’re one of the most common ones. You don’t have to see live fleas for them to be causing a problem for your pets.