Why Is My Dog So Itchy?

 

5/23/17

What is causing all that scratching?

 

All the veterinarians and staff at Family Pet Animal Hospital are pet owners and know how hard it is to watch your pet be uncomfortable in his/her own skin, literally! Just like humans, all pets will have an itch they need to scratch from time to time.  However, if your pet is frequently scratching, biting, rubbing, and licking himself/herself, he or she is likely suffering from one of the following problems:

  • Allergies:
    • Contact allergic dermatitis
    • Flea allergic dermatitis
    • Food allergies
  • Infection: Bacterial or Fungal
  • Skin Parasites

Itchy pets can be a frustrating experience for pets, pet owners, and veterinarians alike.  Keep in mind that there are entire books written on each category of issues listed above.  While our feline friends can also be itchy and suffer from similar problems as dogs, this post will focus on dogs in order to limit the scope.  Here, we examine the most common causes and treatments for all that itching and scratching in your dog.

 

Common Types of Allergies

Allergies often manifest as itchy skin with your pet scratching, biting, and licking especially under the paws and tail, conjunctivitis, and/or chronic ear infections.  Allergies can lead to skin infections due to a disruption of the immune system of the skin and the self-trauma caused by all of the licking and scratching.  These infections often manifest as red and flaky skin, scabs, and pimple-like pustules.  (See section below on bacterial and fungal infections for more information.)

It is important to note that most allergies are inherited, and while they can be managed, they cannot be cured.  Here are the most common types of allergies making our dogs itchy, methods of diagnosis, and courses of treatment.

 

Contact Dermatitis – Allergic or Irritant

Contact dermatitis is a skin condition that can occur when a dog’s skin reacts negatively after making physical contact with an allergen.  While allergic contact dermatitis and irritant contact dermatitis are technically two separate conditions, they are often grouped together because symptoms and treatment are typically quite similar.

Allergic Contact Dermatitis

Allergic contact dermatitis occurs when a pet becomes hypersensitive to substances in their environment, including substances that are seasonal, such as pollen (from weeds, grasses, and trees), molds, and dusts.  Allergies develop after a period of repeated exposure and sensitization and therefore typically develop between the ages of 1-3 years of age.  Due to the extreme seasons and the myriad of various allergens presented in those seasons, allergies are a common problem in Chicago.  Typically, the worst seasons for contact allergies are spring and fall, but can be a year-round problem.  Pay attention to the time of year and watch for patterns in flair ups of itchy skin.

Veterinary dermatologists can perform intradermal allergy testing (AKA “skin testing”) to determine what specific things in the environment are making your pet itchy.  More importantly, skin testing provides the information needed to custom formulate an allergy injection designed to desensitize your pet to the offending allergen.  Treatment with these custom injections is called allergen specific immunotherapy.

Allergen specific immunotherapy is a long-term treatment option which generally takes 3-12 months to reach maximal effectiveness.  As with people, allergy injections are not effective for every pet.  When allergen specific immunotherapy is successful in controlling allergy symptoms, while it may be possible to extend time in between doses, treatment will be necessary for the lifetime of the pet.

Irritant contact dermatitis

Unlike allergic contact dermatitis, irritant contact dermatitis does not require a period of sensitization and can occur from your pet’s first contact with a substance.  Examples of common chemicals and substances that cause irritant contact dermatitis are household cleaning chemicals or detergents, insecticides, poison ivy sap, and road salt.  Certainly, if you can easily identify the offending irritant, eliminate it from your pet’s environment entirely or minimize exposure.

At-home care

If your pet suffers from contact dermatitis, here are some at-home tips to help ease your pets itching that may be utilized in conjunction with additional supportive care treatments recommended by your pet’s veterinarian when necessary.  Ultimately, these are all methods to remove or minimize the irritant or allergen from your pet.

  • Bathing once or twice a week with an oatmeal based shampoo or other product prescribed by your veterinarian for your pet’s condition. Avoid over-lathering, over-fragranced, or drying shampoos, which may exacerbate the problem.
  • Wash your pet’s bedding more frequently. If you’re short on time, you can throw a clean blanket, sheet, or towel over your pet’s bed for the same effect.
  • Use disposable baby wipes to wipe down your pet in between baths to remove the offending allergens.

 

Flea allergy dermatitis (FAD)

Flea allergic dermatitis occurs when a pet develops a hypersensitivity (allergy) to flea bites (specifically flea saliva) and is characterized by severe itching.

Because fleas can survive indoors even during the winter here in Chicago, FAD may be a problem year round.  Typically, veterinarians will diagnose FAD based on the clinical appearance – actually finding fleas, flea dirt, or skin lesions from the flea bites.  For pets with FAD, even a single bite can set off a reaction and a small number of bites can cause severe and prolonged itchiness.  So even though you or your veterinarian may not find a flea or flea dirt on your pet, he or she could still have FAD.

Treatment for flea allergy dermatitis is reducing or eliminating the number of flea bites and can be achieved by a number of products designed for the control of fleas.  Many of the products for flea control recommended by the veterinarians at Family Pet Animal Hospital are combination parasiticides (control various types of parasites such as heartworm, ticks, and/or mites as well as fleas).  Examples of the topical products we use to control fleas are Revolution, Parastar and Parastar Plus.  Bravecto is an oral medication that is effective for 12 weeks against fleas.  Your veterinarian can help you choose the right treatment for your pet based on his/her and your family’s lifestyle.

As with treatment of other causes of itchiness, additional supportive care and medications for secondary skin infections may be recommended by your dog’s veterinarian when needed.

 

Food Allergies

Similarly to humans, dogs and cats may develop hypersensitivities (allergies) to foods.  Symptoms of food allergies are most commonly skin irritation or gastrointestinal issues, such as diarrhea and vomiting.  The most common food allergens in pets are proteins, although virtually any food ingredient can produce an allergic reaction.  While food allergies account for approximately 5-15% of allergies in pets, it is an important possibility to investigate.  Additionally, many dogs can have both food and contact/environmental allergies.

Unfortunately, there is no simple and reliable test to diagnose a food allergy.  Instead, your pet’s veterinarian will recommend a strict food trial where your pet’s diet will be changed to a “novel” or hydrolyzed (broken down into small components) protein for a period of 8 to 12 weeks.  During that time, no other foods, treats, or supplements are to be fed.

The only treatment for food allergies is avoidance of the offending allergen.  Luckily, most pets are successfully treated with a hypoallergenic or other type of specialized diet.

 

Infectious Dermatitis

Infectious dermatitis is the inflammation of the skin caused by various bacterial or fungal (such as yeast) organisms.  Typically, infectious dermatitis does not occur spontaneously – meaning there is usually something else going on with your pet creating conditions for opportunistic organisms to create problems.  In a healthy pet, the skin provides a very effective protective barrier against bacteria and yeast.  However, allergies, damage to the skin (from bite wounds, irritants, parasites, scratching, etc.), autoimmune disease, or immunosuppression caused by certain medications or diseases can all create conditions in the skin that allow yeast and bacterial to invade and cause infections.

Yeast Infections

Malassezia pachydermatitis, which is a type of yeast, is a common culprit of infectious dermatitis.  Infected areas are usually odorous, greasy to the touch, and often affect the ears and/or other areas of the body.   The skin of a dog with a yeast infection can appear red and thickened.  Diagnosis is made via cytology – a sample is taken from the affected area and evaluated under a microscope.  Yeast infections are commonly treated with topical therapy or oral anti-fungal medications.

Bacterial Infections

Staphylococcus is a group of bacteria that are widespread and usually harmless.  However, they are opportunistic pathogens that can invade the skin and cause infections when conditions are right.  Diagnosis of staph infections is typically by visual examination and/or cytology.  The infected skin is often appears red and crusty and pimple-like pustules may be present.  Staph, like fungal disease, is generally treated topically with medicated shampoos, sprays, and/or wipes.  Depending on the severity of the infection, a course of oral antibiotics may be prescribed as well.

While yeast and bacterial skin infections are responsive to treatment, the underlying cause – parasites, allergies, skin irritants, or other medical conditions – must be addressed.  Pets with underlying causes of itching will scratch and damage their skin.  The skin is then prone to infection, which causes more itching.  The underlying cause of the itch must be addressed to halt the cycle of scratching and infection.

Ringworm

Ringworm or dermatophytosis is a contagious and zoonotic (can be transmitted to humans) parasitic fungal infection that can cause red and/or darkened skin, poor hair coat, hair loss (alopecia), often in patches, and severe itching.  Unlike Malassezia and Staphylococcus discussed above, ringworm is typically a primary problem.  Treatment of ringworm requires oral or topical anti-fungal medications and environmental cleaning.

 

Skin Parasites

While dogs can get the occasional bite from mosquitoes, biting flies, or other common insects, these types of bites do not frequently cause severe itching.  As discussed previously, fleas, specifically flea saliva, can be the cause of an allergic reaction.

Sarcoptic Mange

Sarcoptes scabiei mite

Sarcoptic mange or “scabies” in dogs is caused by the Sarcoptes scabiei mite.  This type of mite burrows into the skin of its host and causes severe itching.  The resulting scratching can cause a loss of fur, red, irritated, and/or crusty or thickened skin.  It should be noted that scabies is highly contagious and zoonotic.

Sarcoptic mange is diagnosed by a skin scraping examined under the microscope.  Unfortunately, it is common not to see the mites when performing a skin scraping because the mites can burrow deep into the skin and it only takes a few mites to cause significant itching.  Therefore, a presumptive diagnosis may be made based on clinical signs and ruling out other potential causes of your pet’s scratching.

Luckily, sarcoptic mange is treatable with a combination of therapies to resolve the infestation.  Your pet’s veterinarian will determine what treatment is right for your pet.

Demodectic Mange

Demodex canis

Demodectic mange is an overgrowth of the Demodex mite and is the most common form of mange in dogs.  All dogs have some of these types of mites on their skin, but a properly-functioning immune system keeps the numbers in check and they cause little to no harm to the dog.  Demodectic mange most often occurs in young dogs with immature immune systems or adult dogs with defective immune systems, which allows the numbers of skin mites to increase rapidly.

Demodectic mange is not contagious and is transmitted from mother to puppy during the first few days of life.  Interestingly, demodectic mange does NOT typically cause severe itching, although it does cause hair loss, generally in patches, especially on the face and around the eyes.

 

French bulldog with Demodex

 

A veterinary technician will examine skin scrapings under a microscope. A higher than normal number of demodex mites confirms the diagnosis.  Your pet’s veterinarian will determine the proper course of treatment, which may include topical and/or oral medications.

 

 

Summary

If your pet’s skin and coat are not in optimal health and he is scratching, biting, licking, rubbing and chewing, it’s probably making both of you crazy.  Be sure to have your pet seen by his veterinarian because he surely is not feeling well.

The process of determining the cause of your pet’s itch may take a good deal of time and multiple visits to your veterinarian or a specialist.  Each category of dermatitis must be evaluated carefully and rule outs made prior to a final diagnosis being reached.  Only then can proper, effective treatment begin.  Resolving these cases often takes time but the rewards are a happy pet, owner, and veterinarian.

 

 

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