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Dermatitis, External Parasites and Your Dog's Skin

Dermatitis in dogs refers to a skin condition that becomes red, sore and sometimes swollen or blistered. Such signs of dermatitis often arise as a result of an external factor that causes inflammation and can lead to an allergic reaction.

One instance of dermatitis is caused by external parasites found in your dog's environment irritating their skin and can result in the development of an allergic reaction.

The skin is the largest vital organ of your dog's body, so it needs to be looked after with care. Dermatitis caused by parasites can lead to the disruption of your pet’s natural skin barrier, which is the first line of defense against even more pathogens and secondary infections.

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Where Do External Parasites on Dogs Come From?

External parasites, such as mange (mites), fleas, ticks and lice can be transferred to your dog from other pets and objects, such as dog beds, rugs, sofa and soft toys.

What Are the Common Signs of a Parasitic Reaction?

Two common causes of parasitic dermatitis include flea bites and mange (mites).

Here are some of the common signs that a parasite has infested your dog:

  • Hair loss
  • Redness
  • Itching
  • Scratching
  • Licking and chewing their skin
  • Discoloration (if licking has occurred)
  • Crusts or scabs
  • Odor
  • Contact Your Veterinarian

    Though the signs of parasitic reactions can be similar, your veterinarian will likely be able to understand what is affecting your dog by looking at where on your dog's body the reaction is occurring.


    If your dog is scratching more than usual, particularly from the lower part of their back and down to their tail, they may be suffering from flea allergy dermatitis.

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    If your dog is suffering from mange they may show signs itching around their ears, belly and joints.

    What Is Mange?

    Mange refers to skin diseases caused by mites and can be split into two types: Sarcoptic Mange and Demodectic Mange.

    Illustration of a dog with sarcoptic mange

    Sarcoptic Mange

    This type of mite is not visible to the eye as it typically burrows underneath the skin. Sarcoptic Mange is very contagious so if your dog is suspected to have this, it is best to separate them from any other pets in the household while you manage the infestation.

    Illustration of a dog and a puppy with demodectic mange

    Demodectic Mange

    If your dog has been raised by their mother during the first few days and weeks of their life they will likely have had this mite transferred to them by their mother. For the most part, this type of mite doesn't have any effect on dogs, however if there is a change in your dog's immune system this could potentially lead to the mites causing a serious skin disease.

    Illustration of a flea


    Fleas are tiny insects that attach themselves to animals, such as dogs, to feed. Fleas can result in your dog itching and scratching repeatedly to relieve the irritation caused by the bite. In some cases, an allergic reaction may occur, known as flea allergy dermatitis. Commonly are found around the ears and the tail, you can regularly check your dog for fleas by regularly grooming with a small comb.

    Illustration of lice


    Lice are tiny organisms that can be found in your dog's hair and attached to their skin. Lice on your dog can cause itching and hair loss if not found and managed quickly.

    Illustration of a tick


    Like fleas, ticks also feed off the blood of animals, such as dogs. Again, it's important to check your dog regularly for ticks as if not removed properly and quickly may lead to serious illnesses, such as Lyme Disease. 

    Illustration of a vet with a dog and its owner

    How Might Veterinarians Manage Parasites?

    Once your veterinarian has identified the type of parasite that is causing a reaction, they will be able to recommend management options.

    Fleas - If your dog is suffering from fleas, a veterinarian may recommend a flea control product to first remove the existing parasites from their coat. You will likely also need to treat your home to remove existing parasites and stop the reproduction of future fleas.

    Mange - If diagnosed with mange your veterinarian will recommend the appropriate management to remove mange from your dog's skin. They will likely also suggest different methods to heal and strengthen their skin. 

    For advice, make sure you speak to a veterinarian who will be able to provide a detailed plan of action to support your dog.

    Understand How Parasitic Allergies Can Affect Your Dog

    Increase your knowledge of how parasites can cause allergies for your dog with these short frequently asked questions.