Flea Allergy in Dogs: Flea Allergy Dermatitis, Hot Spots or Biting Sensitivity

Itchy dog
Wyatt Robinson
Written by Wyatt Robinson

As we notice something that strange and terrifying, as open wounds that cover large parts of our dog’s skin, we are likely to believe that it is some scary disease that attacked him. We start to panic, and think that some deadly disease attacked our best friend. In those moments, we forget that the most present illnesses of this century are allergies.

Nowadays, that is a well known fact. Reasons for that can be numerous, but we have only the presumptions. Is it like that because we’ve gone too far with personal hygiene? Maybe it is because of the pollution? Maybe everyday stress leads to that natural response of our organism? Probably all of these matter, but if there wasn’t any progress in diagnosis, there wouldn’t be these presumptions, either. It is certain that there are many cases of flea allergy in dogs. It is a common problem, and it can be controlled.

Allergy is defined as an abnormal reaction of the body to an inside or outside irritation that came from an allergen. That includes immunological response of the whole organism, with all it’s forces, and in some cases, it can lead to serious complications. If treated well from the moment you notice the changes, flea allergy won’t lead to that.

You don’t have to seek for the signs of this allergy in dogs, since the presence of this allergy is followed by characteristic and very noticeable appearance. If you take proper care on time and prevent this from happening, you may never have to face these problems. However, sometimes only one flea bite is enough to start the whole thing, so maybe some of us may find themselves really helpless about it.

Why does it happen?

Mostly in the summer and fall, when the circumstances are suitable for life of fleas, we are exposed to the risk of facing scary moments with our dogs. The flea allergy starts suddenly, and can’t be predicted. The sick animal looks very bad. When we see a dog in that condition, we surely don’t say: „Oh, see, the dog flea allergy!

A bit hard to fight with, but if you take exact measures that are needed, and stick to some efficient way of prevention, it can be cured, and may never come back“! No, it probably gives us headache! That certainly is good. That means that most of us won’t start medication or any invasive treatment by themselves, but will take the dog to a vet, and get the best possible advices on how to react, and the prescriptions that we probably need.

No matter if we intend to treat our dog with natural remedies or medical preparations, the best first step we can make in this situation is consulting a professional about this.

Fleas are world’s number one trigger for allergy dermatitis at dogs. The thing that your dog’s organism can’t tolerate is not the parasite, but its saliva, injected directly under the dog’s skin. That biochemical substance initiates the immune system to give the response and to fight back. They use their saliva to dilute dog’s blood, to be able to suck it faster, and to digest it more efficiently.

They inject their saliva in the micro wound in dog’s skin. Many dogs are sensitive on their saliva or defined more precisely, to the compounds that are called haptens.

Dog itching

If your dog is having his first encounter with fleas, then it won’t lead to allergy. The allergic reaction happens when the dog has been sensitized to this component, and the antibodies in his body are formed in a number large enough to fight the component. It probably won’t happen to puppies and dogs younger than 6 months.

It is threatening mostly to the dogs that are 3 – 6 years old. The older the dog, the bigger is the problem. It can happen to dogs of any sort and gender. If the owner doesn’t react on time, it can take place as a big problem and be considered as serious illness.

One bite is enough to challenge your dog’s immune system and to make a reaction. It is interesting that the dogs that have this hypersensibility have usually very few of these parasites on themselves. That is because they are chasing them away too fast by their grooming activity that becomes so excessive if being irritated this much. But only a few flea bites are enough, on basis of every two weeks, to cause allergic reaction, and to keep that as a sustainable state of your dog.

Symptoms of dog flea allergy

The symptoms are easy to notice, even if the dog is spending most of his time in the yard. The main signs are:

  • Flea dirt (excretion)
  • Fleas, or at least one of them
  • Scratching, licking and biting
  • Hair loss on his back and tale root
  • Redden skin
  • Scabs and hot spots
  • Self injuries

If it lasts longer, without applying any proper treatment, than this can happen:

  • Thickened skin
  • Hair loss expands on other parts of the body
  • Hyperpigmentation ( dark spots)
  • Inflammatory skin infections (bacterial infections)
  • Anemia (due to blood loss and immunodeficiency)
  • Numb incisors (front teeth)

The first symptom is scratching. What comes next is partial alopecia (hair loss), usually on his back and tail, with expanding tendency to abdominal region and legs. There is possibility for appearance of papules, ulcerated skin, often even purulent (pustules).

It is a very itchy, very unpleasant condition. Followed with scratching, enormously often and enormously hard, it leads to making self injuries. If that happens, then it causes further infections and complications. The dog is nervous, tired, and doesn’t stop scratching and biting himself.

Please keep in mind that your dog may be itchy for other reasons. Here’s a great article on some of the other common skin allergies that may be affecting your dog.

When you visit a vet

If this condition occurs, it is your obligation to take your dog to the veterinarian. He will prescribe the most appropriate dog flea allergy treatment for your pet.


We should never make a diagnosis by ourselves, but the vet will find it useful if we know a few things about our dog. First of all, the owner usually knows some details about when, where and how did it all start. The owner of a dog should also check if there are fleas or their excrement on the skin and fur of the dog. The most common and the easiest way to do this is a “white paper test”: put a paper below the dog, and rub the fur roughly, to make the fleas fall down.

If you don’t see them on the paper, and you see tiny brown spots, that will do enough for the evidence. Now, try to moisten the spots that fell onto the paper, and rub over them with a piece of cotton wool. If it turns red, you can be sure you’ve traced the parasites. That is their excrement, and it contains of half digested blood cells. Characteristic physical condition, parasites or their excrements found with white paper test, and positive allergy probation on skin are the ways to prove this allergy.

Dog with allergies at the vet

This allergy is the most often problem with dermatitis at dogs. Vet will exclude all other possible illnesses, like allergies on dust, food ingredients, other parasites, and if needed, take blood of a dog and do the analysis on presence of antibodies. In most cases, there is no need for doing this test, but it can be done if required.


Because of the self injuries (injuries that one made to himself), there is great opportunity for bacterial and yeast infection. Warm and humid spots like these wounds are perfect base for cultivation of many microorganisms. If that happens, then antibiotics must be included in therapy. That is not the thing you can do on your own. You will need a prescription from veterinarian for that.


  • Get rid of the menace: Do this in a bit aggressive, the fastest and most efficient way, using repellents. We should focus on our dog, house and yard. It is important not to overlook if you are having a cat! Cat’s fleas can come to your dog very easy and continue the circle of these unwanted reactions! We should be careful when choosing a repellent, knowing that some of them can cause allergies, too.
  • Prevent further biting and scratching: If the allergy caused open wounds, it will probably be necessary to include antihistaminic and steroids in curing treatment, to make the wounds heal faster.
  • Vacuum clean your house every day: This should be done often, because your dog can bring fleas into the house after a walk, and there are also the cocoons with their offspring tucked in your carpet.
  • Brush your dog very often. This is the way to notice if the dog is infested with these annoying parasites, and it is also a great hygienic practice. This should be done every day, while bathing schedule depends on the kind of a dog and sensibility of his skin. It is recommended to examine your dog more times a week, especially when you come home after long walks, from a forest or a park.
  • Wash your dog’s pillow and blanket. You should do this once a week, using dishwashing soap. It is known that it kills fleas.


The dog with this immune response to a flea bite is not going to lose that reaction ever. He will be allergic on it for all his life. His hair will probably grow again, but if the skin was affected that deep, that it destroyed the follicles of hair, then it can be a permanent hair loss. The sooner you react on the changes, the easier your dog will heal. If you can prevent these states, that would be the best thing for you, your dog and your house.

Use the best repellent against fleas

The most important battle in the war against them is choosing the way of prevention wisely.

It should be efficient, but used carefully, and with a measure.

  • Nitenpyram Capsules: Nitenpyram kills first fleas in about 30 minutes from swallowing the pill, while the last ones die in about 7 hours. It is a short lasting treatment. If you want to get long term effects, combine with:
  • Lufenuron Capsules: After consuming this pill, lufenuron is stored in the fat of your dog. It holds fleas from hatching eggs on your dog. Used together with Nitenpyram, it provides complete prevention, and the effect of one pill lasts one month!
  • K9 advantix II: It kills fleas and ticks, and remains active even after swimming. You get 6 doses in the pack, and the protection of 1 dose treatment from flea infestation lasts at least for 4 weeks!
  • Double row flea comb: This is a thick, double toothed comb, for combing your dog’s hair. It efficiently throws out the fleas, as well as their eggs. The first row loosens the hair, while the second row pushes the parasites out.

You could also consider using specialized shampoo to ease his itching, of which you can find a great list of in our article on dog shampoo for allergies.

Use natural remedies

Here are some non – invasive treatments, and some natural preparations that can help us to keep these tiresome invaders on distance, for a while:

Flea collar

  • 3 – 5 drops of cedar or lavender oil
  • 2 tablespoons of water
  • bandana

Mix these two and rub it in a bandana, and then tie the bandana around your dog’s neck. Repeat this every week. You can even apply the same mixture at the base of your dog’s tail, but don’t put more than 5 drops there.

Flea spray

  • lemon juice
  • water

Mix these two in the same quantities, and rub in the dog’s fur. Focus on these areas:  Behind ears, around the head, on the base of the tail, under the legs.

Flea collar

Rub it thoroughly, that it reaches the skin. This should be done three days, once daily.

Rosemary dip

  • 2 cups of rosemary leaves
  • 4 gallons of water (for big dog)

Cover rosemary with 5 cups of water and let it boil for 30 minutes. Add more water if needed, to cover the leaves. Strain the liquid, add up to 4 gallons of water and let it cool slightly. Pour the water on your dog and rub it in the fur. Let it dry, don’t wash it.

Flea-deterring drinking water

Put about 15 ml of apple cider vinegar into your dog’s drinking water, the amount of water for that day. Do it once in few days.

Flea control in the yard

Protect your yard from flea invasion by spreading cedar chips around, especially in the places where your dog usually sleeps, or spends most of his time.

If you’d like to know more about the flea life cycle and how to effectively get rid of them, read ahead in our article about flea and tick control.

What is the dog flea? Is that an insect?

Dog flea (Ctenocephalides canis) is a wingless brown or yellowish insect, an ectoparasite (parasite that lives on the body of a host, not in it), about 1,5 mm – 2,5 mm long, pressed on the sides, to be able move easier through thick fur of a host.

They can jump vertically about 7 inches, and horizontally up to 13 inches, so it can pass over from an animal to another animal without any mutual physical contact of these two. There is no need to avoid contact with others, because that is not the way to protect your pet from flea infestation.

Flea life cycle


It attacks our pets frequently, and is very unpleasant for us, for our pets, our house and yard. When it once settles on your dog, it lives on his blood, and lays eggs on his hair and skin.

  • Flea eggs: Eggs are not sticky, and they fall down on your carpet, dog’s bed, around the house, and around your yard. They are white and small as a grain of sand. An adult flea can lay about 40 eggs a day. If the temperature and humidity is suitable for their development (around 70-85˚F, and 70% humidity), it takes them few days to develop into larvae. If the conditions are not that fine, they can stay in the state of eggs for few weeks.
  • Flea larvae: White and wormlike, they can wait for months in this phase. They are mobile, and tend to avoid light. They survive eating flea dirt that can be found around the places where your dog spends his time. Larvae become pupae, when they complete 3 stages of their development. At the end of the third stage, they form an encrusted cocoon around themselves, and they are now called pupae.
  • Flea pupae: They can hibernate in their cocoon up to 170 days (whole winter), and they wait hidden and tucked in surfaces like your carpet or a couch, or your dog’s bed. When the time comes, and they register vibrations, heat and pressure, they wriggle out of their ambush and their cocoon, and hook on their host. They are able to feed a day after they emerge. You can’t kill pupae with insecticides. Any treatment that will help you to get rid of the fleas, their larvae and eggs, won’t kill pupae.
  • Adult form: When they finish their first meal, they mate, and tomorrow, they lay their eggs around in bunches of 20 – 40. They will do it every 24 – 48 hours, 100 days of their life!

Fleas as mechanical vectors (flea-borne diseases)

The fact that their body liquid comes into direct touch with the blood of their host, makes them possible vectors for transmitting serious illnesses like murine typhus, bubonic plague (those fleas were found on rats), or pasteurellosis, and parasites like heartworm or tapeworm, if chewed and swallowed. Therefore, even if your dog is not hypersensitive on their saliva, you should prevent him from being infested with fleas, because it is the best way to save the dog and the environment from bigger problems.

About the author
Wyatt Robinson
Wyatt Robinson

Wyatt Robinson had a great 25-years career as a veterinarian in United Kingdom. He used to be a member of British Veterinary Association and worked in 3 pet hospitals in London and Manchester. He is shining when he sees his pets healthy and full of energy and it is his duty to help other dog owners to keep their best friends full of life.