dog covering face with paw

How to tell if a dog has fleas

LAST UPDATED February 2024

This article is written by Pet Circle veterinarian, Dr. Jenny Eales BVSc (Hons)

Every year, millions of dogs suffer from the discomfort of flea infestations. These tiny parasites not only cause severe itching but can also lead to serious health issues if left untreated. Many pet owners are unaware of the infestation until it's too late, leading to prolonged discomfort for their beloved pets and potential health risks.

Imagine your furry friend constantly scratching, losing hair, or developing infections, all while these tiny pests thrive on them. It's not just about the physical toll on your dog; the emotional distress of seeing your pet suffer can be overwhelming. Plus, an untreated flea problem can quickly spiral out of control, spreading fleas throughout your home, affecting other pets, and even posing risks to human inhabitants.

Fortunately, recognizing the early signs of flea infestations and implementing effective preventive measures can spare both you and your pet from this ordeal. In our comprehensive guide, we'll explore proven methods to detect, treat, and prevent fleas, ensuring a happier, healthier environment for your four-legged family member.

In this article:

Fleas basics
Why do we need to treat fleas?
Symptoms of flea allergy in dogs
Methods to check your dog for fleas
When to seek help
Treatment and prevention
Further Reading

Understanding the Menace - Flea Basics

flea under microscope

Fleas are small, wingless, bloodsucking insects that live on your dog's body and lay eggs in the environment. They feed on the blood of animals and humans. After a blood meal the females lay eggs either on the host animal (which fall off into the environment) or in the environment nearby, where the rest of their life cycle takes place.

Believe it or not, the flea that you are most likely to find on your dog is the cat flea (Ctenocephalides felis). The dog flea (Ctenocephalides canis) is much less common in Australia, but is occasionally found. Despite your best efforts, your dog may become infested with fleas through contact with other animals, or fleas that are roaming around in the environment.

There are four life stages of a flea: egg, larvae, pupae and adult. Of all these phases, only the adult phase occurs on the host (your dog!). Eggs are laid in the environment - particularly in soft warm fabric such as carpets, pet beds, and blankets. This is why it's so hard to get rid of fleas: a new wave of juvenile fleas can emerge after you've killed the initial population with a flea treatment.

flea life cycle

Why do we need to treat fleas?

Fleas don't just annoy dogs, they can also spread disease to dogs and other animals, as well as humans. They carry the flea tapeworm, which your dog can get as they groom themselves and ingest the flea. Heavy flea burdons can cause anaemia (especially in young, sick or elderly dogs) and intense itching in pets. Dogs with flea allergy dermatitis are especially affected.

Flea allergy dermatitis (FAD) is a condition in which dogs are allergic to the saliva of fleas. It can develop at any age and results in excessive itching, scratching and hair loss which can lead to wounds caused by self trauma, and skin infections.

Symptoms of flea allergy in dogs

For dogs allergic to fleas, just one bite can cause intense itching. This makes the dog scratch, chew and lick their skin to the point where they cause self trauma. They may also rub their body along walls and other objects and may appear restless and uncomfortable.

If your dog has a flea allergy you may see the following:

  • Hair loss
  • A red rash or small red pimples or bumps
  • Small scabs
  • Thickened or discoloured skin
  • Scratches or wounds from self trauma
  • Fur stained brown, which is saliva staining from them licking constantly

These signs are usually seen along the lower back and base of the tail, the thighs and the belly, but in severe cases can be seen all over the dog.

If these symptoms are left untreated, your dog may lose more hair and continue to traumatise and damage their skin. Licking and chewing constantly leaves moisture on the skin that can lead to yeast and bacterial infections, such as "hot spots" or pyoderma, which need veterinary treatment. It is also very distressing for dogs to be constantly itchy, and can affect their mental wellbeing.

sad dog lying on bed

Methods to check your dog for fleas

You can usually see signs of fleas (but not always the fleas themselves).

1. Visual Check:

Fleas resemble little red or brown ovals and are approximately 1-3mm long. They are very fast moving and can jump up to 48 cm horizontally and up to 20cm high, so you might not always see them.

The best place to look for live fleas is over your dog's rump and around their tail base. If you cannot find any, it doesn't mean they aren't there, it just means you should look for signs they are there rather than the fleas themselves.

2. Flea Comb Method:

A flea comb is a special comb that has teeth which are very closely spaced so they can trap fleas, flea eggs and flea dirt.

To use a flea comb to check to detect the presence of fleas:

  1. Begin at your dog's head and comb towards their tail, in the direction of the fur growth.
  2. Check the comb regularly for fleas or flea dirt.

Flea dirt looks exactly like its name suggests - small dark brown or black crumbly dirt. What it actually is though is flea faeces (gross!) i.e. digested blood. They turn a rusty or red colour if they come in contact with moisture - this is the digested blood.

To check for flea dirt you can use the white towel test:

3. White Towel Test:

There are 2 ways to do this test. Essentially you are looking for flea dirt or flea faeces.

  1. Brush your dog while they are standing on a white towel or sheet. Spray water on any small brown or black particles that fall off. Flea dirt will turn red or rust coloured when exposed to moisture.
  2. Use a flea comb and collect any brown or black specs that fall off, put them on a white paper towel and spray with water. If it turns red or rusty coloured it is flea dirt.

When to seek help

If your dog has fleas, do you need to take them to your vet? It is recommended to do so if the following occurs:

  • If you cannot get your dog's flea infestation under control
  • If you suspect your dog has a flea allergy
  • If your dog is extremely itchy and you are worried they will injure them self
  • If your dog has scratched themselves so much that they have injured them self, they have a rash, areas of fur loss, or skin wounds/infections

Does my dog have fleas or allergies?

There are tests available to confirm flea allergy, such as intradermal skin testing which is usually performed by specialist veterinary dermatologists. There are also some blood tests available to check for allergies.

In most cases, FAD can be diagnosed using the dog's history and examining the clinical signs the dog has (such as itchiness and fur loss in the "flea triangle" (the middle of the back to the tail base and the rear legs)).

Other causes of itchiness in dogs include (but are not limited to) the following:
Food allergies
• Contact allergies
• Atopic dermatitis
• Other parasites like mites
• Fungal infections (e.g. ringworm)

Treatment and prevention

It is important to make sure your dog is on a reliable flea prevention year round, to break the flea cycle especially if they have FAD. It is also extremely important to treat the environment as only 5% of the flea life cycle is carried out on your dog,with the other 95% occurring in the environment.

Common flea prevention products

Flea prevention products can be in the form of tablets, chews, topical spot ons or collars. Some products prevent fleas only, some prevent fleas, ticks and mites, and some are "all-in -one" type products that prevent fleas, ticks, mites, heartworm and intestinal worms.

Flea shampoos and flea powders are available but are not as effective for flea control as other products.

For very young puppies with fleas, or puppies that are too small for preventatives, it is best to ensure mum is on a preventative that is safe to use while lactating (if the puppy is still with mum) and use a flea comb on the puppy to gently remove any fleas.

Don't forget to treat the environment, not just the dog!

As 95% of the flea life cycle occurs in the environment, treating the environment is an important part of flea prevention. Eggs, larvae and adult fleas will drop off your pet into surrounding areas of the house. If you have an infestation of fleas, you will need to wash their bed, blankets and stuffed toys. Use a hot wash (60°C) with regular washing detergent and if possible, place items in the dryer on a hot cycle. Carpets will need to be vacuumed or steam cleaned. The vibrations from vacuuming will help to stimulate the pupae in the environment to hatch so that you can suck up the adults before they get a chance to bite!

You can use flea bombs to kill the parasitic trespassers in your home. Flea bombs are for the environment only and are not to be used to protect humans or animals.

If you have multiple pets in the house, dogs and cats, treat all of them. Treating one of, or half your pet population will not be enough. When you give your dog a flea treatment, it treats your dog, not the environment. Untreated pets will be a breeding ground for fleas which will just transfer to the environment causing another infestation.

Preventative measures to reduce the risk of future infestations

The best way to prevent future flea infestations is to keep all of your pets on flea prevention all year round, as well as treating the environment if fleas are present. This way, no new flea eggs will be laid, so over time there will be less larvae and pupae living in the environment leading to less reinfection of your pets.

It is also important to weigh your dog before treating them to make sure you are using the correct dose to be effective. If you are using a spot- on prevention, please make sure to follow the instructions about bathing and swimming as exposing your dog to water too close to the application of spot on products can greatly reduce their effectiveness.


How long do fleas live?

Adult fleas can live for 2-3 months, but the larvae can lay dormant in the environment for up to a year!

Can I get fleas from my dog?

Fleas can get onto humans and bite us, but they cannot survive on us as we don't have enough hair. For more information, read through Can Humans Get Fleas from Dogs?

What do flea bites look like on dogs?

Flea saliva contains histamine-like substances along with other enzymes that can be irritating or allergenic. So, dogs that are hypersensitive to flea bites can become very itchy, which can lead to excoriation (erosion or ulceration of the skin) and skin infection caused by self-trauma. This can lead to noticeable lesions such as pustules (a raised lump containing pus), papules (a solid, raised area of skin, less than 10mm in diameter) and epidermal collarettes (circular lesions with a rim of scale, crust or an edge that is peeling).

Can fleas cause hair loss in dogs?

Yes, flea infestations can cause hair loss in dogs. When fleas bite a dog, their saliva contains histamine-like substances, which can lead to skin irritation and itching. Dogs may scratch, bite, or lick the affected areas excessively, leading to hair loss. Additionally, some dogs may develop an allergic reaction to flea saliva, known as flea allergy dermatitis, which can exacerbate the itching and hair loss.

Why is my dog's flea preventative not working?

If you have used a flea prevention, but your dog is still scratching or your are still seeing fleas or flea dirt, this may be due to a number of things. Firstly, if there is an established flea population in your household, it can take several months of strict flea control to control all the flea life stages. In this case, environmental control (as detailed above) will help you work through the environmental population more quickly. Alternatively, it may that you've given the wrong dose so make sure to weigh your dog before treatment. There may also be another pet with fleas that are laying eggs in the environment and reinfecting your dog, so make sure that you treat all of your pets for fleas.

Further Reading

Want more information? Check out some of our other articles:

Identifying Paralysis Ticks on Dogs and Cats
How Often Should I Worm My Dog?
Heartworm in Dogs
Best Flea and Tick Treatments for Pets
Do Tick Collars Work?
How to Get Rid of Dog Fleas