Sep 01 2015

Why is my dog itchy?

Cat Playing With Dog Tail

As the seasons change, we are beginning to see more patients with itching and rashes at Mobile Veterinary Clinic. What does it mean if your dog has a rash or is very itchy? Unfortunately, there are seemingly infinite causes for itching in our pets. It can often take a great deal of time to find the underlying reason for itching and sometimes, we never get a definitive diagnosis and must make assumptions regarding further treatment.

The 5 most common causes of itching are listed below*:

  • Staphylococcal dermatitis
  • Yeast (Malassezia) dermatitis
  • Ringworm (Dermatophytosis)
  • Ectoparasites- mites and fleas especially
  • Allergies- fleas, food, and, environmental.

The doctors at Mobile Veterinary Clinic approach itching in a very systematic fashion. The appointment for an itchy dog starts with getting a very detailed history. You may be asked some of the following questions:

  • When did the itching start?
  • When was the last time your pet was normal?
  • How itchy is your pet on a scale of 1-10 (1 being not itchy and 10 being very itchy)?
  • Was the onset of the itch sudden or gradual?
  • Has your pet ever had any skin or ear problems before? If so, when did these problems begin?
  • If treatment has been done previously for the same problem- what did it consist of and how did the pet respond?
  • Has the rash changed in appearance with time or has it remained the same?
  • Does your pet have any previous medical issues or surgeries?
  • Do you have any other pets? Are they showing similar signs?
  • Do you have any rashes too?
  • Has your pet had any exposure to other animals lately?
  • Is your pet on flea/ tick control?
  • What food is your pet on (Brand and type is important!)
  • Does your pet go swimming on a regular basis?

Yes. It is A LOT of questions, but it helps give us a great deal of information so we can figure out the best way to go about treating your pet!

After getting a detailed history, the doctors will perform a full physical exam and then a full dermatological exam. They will note all of the abnormal areas of skin and may even draw pictures to help map out all the skin lesions on your pet. In addition, the doctors will look specifically for external parasites like fleas.

 

Some external parasites , like mites, are microscopic. There are usually two mites that the doctors are primarily looking for: Demodex and Sarcoptes (scabies). Your veterinarian may recommend doing what is called a skin scraping to look for mites. This tests consists of using a dull razor blade with mineral oil to scrape the surface cells off the skin. There are two different methods of skin scraping. The first is called a deep scrape. The skin is pinched and then scraped until capillary bleeding is obtained. This may cause a bruised looking area on your pet. Unfortunately, this is the only way we can find the Demodex mite as it lives deep within the hair follicles. On the other hand, scabies mites are often few and far between. A superficial skin scrape is performed in which just the very surface of the skin is lightly scraped. Unfortunately, even if we scrape an entire dog, we may never find the culprit mite. One Sarcoptes mite can bite the skin and cause a terribly itchy reaction and then never be found. If the doctor is suspicious for Scabies, they will often times place pets on a prophylactic course of anti-parasiticides. Scabies can be zoonotic (able to be transmitted from animals to people). The veterinarian may ask if you have found a rash and recommend going to see your doctor.

Another test the doctor may recommend running is called a fungal culture to evaluate for ringworm. The doctor will take hair pluckings and place them in a petri dish. The petri- dish is incubated for 10 days and the pet is then deemed positive or negative based on fungal growth. If a pet is positive, that pet is placed on anti-fungal medications. Ringworm can be zoonotic (able to be transmitted from animals to people). The veterinarian may ask if you have found a rash and again, recommend going to see your doctor.

What about staph and yeast dermatitis? Just like in people, animals have a normal population of yeast and bacteria that live on the skin without causing problems. This population is called the microflora. The bacteria and yeast only become a problem if there is a change in the normal skin barrier. Once the yeast and bacteria overgrow, animals become very itchy and must be treated with oral or topical antibiotics and anti-fungals.

So what changes the normal skin barrier. The two most common culprits are excessive moisture retention (swimming) or an allergy. Allergies by themselves are itchy but they also allow a change in the normal skin immune system allowing for an overgrowth in the normal microflora. This leads to an even itchier dog! There are 3 main types of allergies. The first is to flea bites. A dog does not have to be infested with fleas to be extremely itchy. Similar to with scabies, one flea bite can set off a terrible allergic reaction but we may never find the culprit flea. The second is to food. Most commonly dogs are allergic to the protein source in a food (chicken, beef, soy, etc.). The only way to diagnose an animal with a food allergy is to do a food trial. Unlike in people, intra-dermal skin testing is very unreliable for food allergies in dogs. A food trial consists of a 12 week diet change to a special food recommended by the veterinarian. The third is an environmental allergy. We usually make this diagnosis by ruling all other causes for itching out. Environmental allergy is the hardest to diagnose and the most difficult to treat as we cannot remove the offending allergens. We usually treat these pets symptomatically and keep them comfortably itchy.

So what do I do if my dog is itching? Because of the nearly infinite possibilities for the etiology of itching, it is best to bring your dog to your veterinarian. Dr. Brianna Reid and Dr. Michael Reid are available 7 days a week to evaluate your pet and can make the best recommendations to bring comfort to your furry friend. Has your pet ever been itchy before? What did you do to help them?

 

*This list does not encompass all the possible causes for itching. Your veterinarian will make the best recommendations for your pet based on his or her individual history and physical exam.*

 

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