PMD Blog – How Do I Know If My Dog Has Fleas?

How Do I Know If My Dog Has Fleas?

Signs to look for, how to check at home, and what to do next.

Quick Answer

Fleas are one of the most common parasites in UK dogs — and you often can't see the fleas themselves.
The most reliable sign is flea dirt: small dark specks in the coat that turn reddish-brown on damp white tissue.
Scratching, biting, and hair loss at the base of the tail are classic signs of fleas.
Even if your dog is treated, 95% of a flea infestation lives in your home — the environment needs treating too.
All pets in the household should be treated at the same time, using products suitable for each animal.

Fleas are small, fast, and very good at hiding. Most dog owners never actually see a flea on their pet — they find out through the signs the fleas leave behind. Knowing what to look for makes a big difference, because a flea problem caught early is much easier to manage than one that's had time to establish itself in the home.

The most common flea found on UK dogs is actually the cat flea (Ctenocephalides felis), which infests dogs just as readily as cats. Dog fleas (Ctenocephalides canis) do exist but are far less common in practice.

Signs Your Dog May Have Fleas

01 Scratching, Biting, or Chewing

Persistent scratching — particularly at the base of the tail, the lower back, belly, groin, and behind the ears — is one of the first things most owners notice. Dogs with a flea allergy may scratch intensely from just one or two bites; others with no allergy may scratch much less despite having many fleas. The absence of obvious scratching doesn't rule fleas out.

02 Flea Dirt in the Coat

Flea dirt is the most reliable sign of a flea infestation. It's the dark, pepper-like specks left in the coat by feeding fleas — and it's essentially digested blood. Part your dog's fur, particularly near the base of the tail and around the lower back, and look for these small dark dots. To confirm: collect a few specks on damp white tissue. If they dissolve to a reddish-brown colour, it's flea dirt. If they stay black, it's just ordinary dirt.

03 Seeing a Flea

Adult fleas are small (around 1–2mm), dark brown, and move very fast. They don't fly, but they jump considerable distances. You're most likely to spot one moving quickly through the fur near the skin, or on lighter-coloured areas of skin or bedding. Most infestations are identified through flea dirt rather than a live flea sighting.

04 Hair Loss or Bald Patches

Repeated scratching and chewing can damage the coat and cause hair loss, usually starting at the base of the tail and along the lower back. In dogs with flea allergy dermatitis, even minimal flea exposure can cause significant hair loss and skin damage. This kind of pattern of hair loss is a useful pointer.

05 Red or Irritated Skin

The skin may appear red, inflamed, or thickened where your dog has been scratching. In flea allergy dermatitis, the skin reaction can spread beyond the actual bite sites. Secondary skin infections — bacterial or yeast — can develop when the skin barrier is broken by repeated scratching.

06 Hot Spots or Sores

Hot spots are areas of moist, raw, inflamed skin that develop when a dog licks or chews intensely at one area. They can appear quickly and spread fast. Fleas are a common trigger, though not the only one. Hot spots need veterinary attention — they're uncomfortable and can become infected.

07 Tapeworm Segments Near the Tail

Dogs can ingest fleas while grooming themselves, and infected fleas can transmit a specific tapeworm (Dipylidium caninum). If you notice small, cream-coloured segments — sometimes described as looking like grains of rice — around your dog's tail or in the bedding, this is a sign of tapeworm. Finding tapeworm segments should prompt you to also check for fleas, as the two often go together.

08 Pale Gums or Lethargy in Puppies

A heavy flea infestation can cause anaemia in very young or small dogs. Adult fleas feed on blood; in a puppy, the blood loss can be significant.

Pale gums, weakness, or lethargy in a puppy with fleas needs urgent veterinary attention.

How to Check Your Dog for Fleas at Home

The flea dirt test is the most reliable way to confirm a flea problem. Here's how to do it:

Stand your dog on a sheet of white paper or a white towel.
Use a fine-toothed flea comb — or just ruffle the coat firmly with your fingers — working from the back end forward.
Look at whatever falls onto the white surface. Focus on dark, pepper-like specks.
Collect a few specks and place them on damp white tissue.
If the specks turn reddish-brown after a minute, that's flea dirt confirming fleas. If they stay black, it's ordinary environmental dirt.

Pay particular attention to the base of the tail, the lower back, the groin, and the belly when combing — these are the areas fleas prefer.

Why Treating the Home Matters as Much as Treating Your Dog

This is the part many owners miss — and the reason flea problems keep returning.

On your dog

Adult fleas — around 5% of the total infestation. These are the only ones you might see.

In your home

Eggs, larvae, and pupae — approximately 95% of the infestation. These live in carpets, sofas, bedding, and floor cracks.

Flea pupae can lie dormant in the environment for months, then hatch when warmth and vibration signal that a host is nearby. This is why fleas can seem to appear suddenly in a house that's been empty, or why treating only the dog rarely solves the problem for long.

What a complete treatment looks like

Treat all pets in the household at the same time — not just the dog showing symptoms.

Treat the home: wash all bedding at a high temperature, vacuum thoroughly (including under furniture and along skirting boards), and use a household flea spray suitable for the environment. Some household sprays contain an insect growth regulator that prevents eggs and larvae from developing.

Follow the treatment schedule your vet recommends. A single treatment is rarely sufficient — the timing needs to align with the flea life cycle to be effective.

Always use products appropriate for the species and age of each animal. Some flea products safe for dogs are toxic to cats. Puppies and pregnant or nursing dogs need products specified as suitable for them — check with your vet.

Contact Your Vet Urgently

A puppy has pale gums, weakness, or lethargy alongside a flea infestation — possible anaemia
A very small or young dog has an extremely heavy flea burden
Skin is severely broken, infected, or showing signs of a serious hot spot
You've used a flea product and the dog is showing signs of a reaction (drooling, tremors, lethargy)

Flea product reactions can be serious. If you suspect your dog has reacted to a treatment, call your vet straight away.

When to Contact Your Vet

You suspect flea allergy dermatitis — intense scratching from minimal flea exposure needs proper diagnosis
Skin is red, thickened, smelly, or showing signs of secondary infection
You've found tapeworm segments — both the tapeworm and flea infestation will need treating
Over-the-counter treatments haven't worked after proper, consistent use
You're unsure which product is appropriate for your dog's age, weight, or health status
The infestation keeps returning despite home treatment

How Pet Med Direct Can Help

Pet Med Direct stocks flea prevention and treatment products for dogs in the UK. Some are available without a prescription; others — including many of the more effective prescription-strength spot-ons and tablets — require a valid prescription from your vet.

If your vet has recommended a specific flea treatment, browse the Pet Med Direct shop to see if it's available. Always use the correct product for your dog's species, weight, and age, and follow the label instructions carefully.

Some flea treatments require a valid veterinary prescription. Pet Med Direct can only supply prescription medicines after the prescription has been checked. Always follow your vet's advice and the directions on the medicine label.

Frequently Asked Questions

My dog doesn't seem to be scratching much. Could it still have fleas?

Yes. Not all dogs react visibly to flea bites — some carry a significant infestation with very little scratching. Finding flea dirt is more reliable than watching for scratching. Check the coat regularly, especially after walks in areas where other dogs or wildlife are present.

I've treated my dog but I'm still seeing fleas. What's happening?

If you're still seeing fleas after treatment, it's almost certainly because eggs and larvae in the environment are hatching and reinfesting your dog. The home needs treating alongside the dog. Vacuuming daily, washing bedding, and using a household flea spray — consistently and over several weeks — is needed to break the life cycle.

Can humans get fleas from a dog?

Dog and cat fleas will bite humans, though they don't live on us. Bites typically appear on the ankles and lower legs and cause small, itchy red spots. Treating the pet and home environment usually resolves human bites as the infestation is controlled.

My dog is an indoor dog. Can it still get fleas?

Indoor dogs can still get fleas. Fleas can be brought into the home on clothing, shoes, or other pets. A dog that goes outside briefly — even just for toilet trips — has some exposure. If visitors bring pets, or if the home had fleas before the dog arrived, this also counts.

Do I need to treat my cat if only my dog has fleas?

Yes. If any pet in the household has fleas, all pets need treating simultaneously. Treating only the dog leaves the cat as a reservoir for the infestation to continue. Always use species-appropriate products — some dog flea treatments contain permethrin, which is highly toxic to cats.

How often should I use flea prevention on my dog?

This depends on the product. Spot-on treatments, tablets, and collars all have different durations of effectiveness. Follow the product instructions and your vet's guidance. Year-round prevention is generally recommended in the UK, as centrally heated homes allow fleas to survive through winter.

← Back to Dog Health Hub

Need pet products or prescription medicines? Visit the Pet Med Direct shop.

Shop Pet Med Direct

This this article is for informational purposes only and does not constitute veterinary advice.
If you are concerned with your dog’s health, please consult a qualified veterinarian.