Dermatitis in Dogs: Causes, Symptoms, and Treatment
Dogs, like people, can develop allergies to a variety of things from pollen and other airborne substances to specific ingredients in their food. Allergen is the general term for the specific substance that causes the allergy. These allergens can cause dermatitis (inflammation or irritation of the skin) due to an immune response in that particular dog when the allergens are inhaled or are absorbed through the dog’s skin. Keep reading to learn more about the most common causes for dogs’ itchy skin and dermatitis, how to determine what’s going on, and treatment options.
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What is dog dermatitis?
The term canine dermatitis simply means inflammation (redness and often itchiness) of the skin. This is a general term that may be used to describe skin irritation caused by any disease. There are many causes of skin inflammation in dogs. Some of the more common diseases that lead to dermatitis are atopy, flea allergy dermatitis, and food intolerance or allergy.
Causes of Canine Dermatitis
There are many causes for dermatitis in dogs, but the more common ones are as follows:
1. Canine atopic dermatitis (also called canine atopy or allergic dermatitis)
This is a complicated disease process where affected dogs may be genetically predisposed to developing atopy. It is estimated that roughly 10% of dogs have atopic dermatitis. Dogs with atopic dermatitis have a defect with their skin’s natural protective barrier. Most of the allergens that cause itching in these dogs enter through contact with their skin and its defective barrier.
Animals with atopic dermatitis have a history of pruritus (i.e. licking, chewing, scratching) that may or may not be accompanied by recurrent skin and/or ear infections. Signs can be seasonal or non-seasonal. They may also start seasonally and then progress to non-seasonal (e.g. year-round).
Dogs with atopic dermatitis often have areas of reddened skin, raised bumps, scratches, crusts, and may have thickened skin from a long history of having dermatitis. The itchy areas in these dogs often include the armpits, lower abdomen, paws and in-between toes, and the area around the dog’s eyes, ears, mouth and lip folds, and bottom.
Most of these dogs start to show signs between 2-6 years of age. As this disease tends to be inherited, multiple breeds are predisposed.
- Commonly affected breeds include:
- Labrador Retriever
- Golden Retriever
- Cocker Spaniel
- Terriers (most, including Pitbulls)
- German Shepherds
However, many dogs including mixed breeds can have atopic dermatitis.
Early skin signs include reddened circular areas, patches, and small bumps. Self-trauma from licking, chewing and scratching can lead to signs of fur loss, wounds, thickened and darker colored areas of skin.
Treatment / Management of Atopic Dermatitis:
- Identification and avoidance of the allergen and infection with bacteria or yeast (often considered secondary bacterial dermatitis or yeast dermatitis)
- Improvement in skin and coat hygiene and care (e.g. bathing)
- Reduction of itching and skin wounds with medications (e.g. topical and/or systemic)
- Targeted therapy of the allergy with intradermal allergy testing and desensitization
Canine atopic dermatitis is a life-long condition that can severely affect both patient and pet owner quality of life. Preventing or minimizing the frequency of skin flare-ups improves patient quality of life and owner satisfaction, as well as lessens adverse effects from prolonged administration of systemic medications. Flare-ups can be lessened by identifying and desensitizing the animal to offending environmental allergens when your veterinary dermatologist performs an intradermal skin test and then formulates an injectable to desensitize your dog to their allergens over time. This immune modification may take upwards of a year to determine its full benefit.
2. Flea Allergy Dermatitis (flea bite hypersensitivity)
Dogs with flea allergies have an allergy to a protein in flea saliva.
Skin issues in dogs with flea allergy dermatitis often appear as small raised bumps and crusts seen over the lower back, above the tail, and inner thigh area. These dogs may scratch their sides, thighs, belly, lower back, neck, and ears. Often these dogs are quite restless and are almost constantly scratching, chewing, and/or licking at their skin. Dogs with long-term flea exposure can have thickened skin that may become a dark grey color and the fur loss may cover most of their body.
The most common signs of flea allergy dermatitis are fur loss and the presence of fleas along with marked itchiness. This type of dermatitis is diagnosed by the skin changes seen and ruling out other possible causes for the skin issues. Signs of itchiness may develop minutes to days after the flea bites, depending upon if the dog has a more immediate or delayed immune reaction to the flea saliva.
Flea allergy dermatitis does not usually occur before 1 year of age. Any breed of dog can be affected. Dogs with severe flea allergies are often found to be nearly “flea-free” due to excessive self-grooming as they are so itchy.
To treat and prevent flea allergy dermatitis, appropriate flea treatment and prevention of flea infestations is a must. Also, proper treatment of any secondary skin infection, resulting in bacterial dermatitis or Malassezia dermatitis, must occur to resolve the dog’s itching.
3. Food Allergy Dermatitis
Dogs who have food allergies typically develop a hypersensitivity reaction to either a protein or carbohydrate in the food or treats that they eat.
The most common sign in food-allergic dogs is itchiness/scratching which may be focused on one or multiple areas of the dog’s body. The more common areas where dogs with food allergies lick, chew or scratch, are their ears, feet, underneath their chest or abdomen, and less often around their hind-end.
Although we won’t discuss this further here, food-allergic dogs may also show GI signs such as vomiting, diarrhea, a marked increase in stools/feces produced, soft to loose stools, straining to pass stool, gassiness, and possible weight loss. These signs are usually noticed year-round unless the food or treat causing the issue is not constantly fed.
Although dogs with food allergies typically develop clinical signs of disease in young adulthood (1–4 years old), the age of onset in dogs has been reported to range from <6 months to 13 years. Thus, a food allergy may be a particularly likely cause for dermatitis in dogs when first seen at either a very young or very advanced age.
Breeds that more often have food allergy issues are:
- German Shepherds
- Labrador Retrievers
- French Bulldogs
- West Highland White Terriers
This does not mean that other dog breeds cannot have food allergies.
For dogs presenting to a vet for dermatitis or itchiness, food allergies may be determined to be the cause for up to 24-40% of cases.
The only reliable way to diagnose food allergies is by performing an elimination diet trial. There are a couple of tests that may help when selecting which foods to avoid when choosing a diet. However, these tests (western blot blood test and skin/patch testing) cannot diagnose a food allergy. The most common sources of food allergies in dogs are beef, dairy products, chicken, wheat, and lamb.
For more information on performing a diet trial please see: How to Perform a Food Trial for Your Pet's Allergies
Other Diseases That May Causes Changes to Your Dog’s Skin
- Mange (from demodex or scabies mites)
- Underlying diseases such as hypothyroidism or Cushing’s disease may predispose a dog to have dermatitis.
Clinical Signs of Dermatitis in Dogs
Dermatitis in dogs can be seen as any combination of the following symptoms:
- Abnormal redness of the skin
- Thickening of the skin
- Dark color (grey/black)
- Fur loss (alopecia)
- Unusual odor
- Excessive oil production of the skin
How will the vet test my dog for dermatitis?
Initially, your dog’s vet may recommend any combination of the following tests to help determine the cause of your dog’s skin issues:
- Medication Trial (antihistamine, Cytopoint, Apoquel or Corticosteroid (steroid))
- Diet Trial (offering a food containing protein and carbohydrate source that your dog has not had before)
- Skin Scrape (checking for mites)
- Skin Biopsy
- Intradermal Skin Testing
- Bloodwork to check for specific allergies, hypothyroidism, or Cushing’s Disease
Veterinary Treatment Options for Canine Dermatitis
The treatment that your vet recommends will depend upon your dog’s diagnosis - either general such as seasonal or environmental allergies, or specific (i.e. flea allergy dermatitis or allergy to soy).
Some of the treatment options that your vet may recommend are as follows:
- Medicated baths with a shampoo made specifically for dogs with dermatitis
- Flea Prevention/Control
- Hypoallergenic diets
- Antibiotics and Antifungals (to treat secondary skin infections if found)
- Immunotherapy (when exact allergens causing the issue have been identified)
What about giving my dog over-the-counter medication for their itchy or red skin?
Do not give over-the-counter (OTC) medications to your dog without talking to your vet first. If not given appropriately or in the right case, OTC medications can be dangerous.
Home Treatment for Dermatitis in Dogs
There are several things you can do at home to keep your dog as comfortable as possible while waiting for your vet appointment and allergy consult. A few safe treatments include:
- If your dog is licking or chewing excessively at themselves, an Elizabethan collar (cone) may be helpful to lessen further damage to their skin.
- If your dog is itchy everywhere, you may bathe your dog with a mild shampoo (i.e. oatmeal-based) daily to every other day. Make sure to use lukewarm water and thoroughly rinse the shampoo away.
- Any individual wounds may be cleaned with a mild soap or dilute betadine solution twice daily and then blotted dry.
Can dog dermatitis be prevented?
It all depends upon the underlying cause of your dog’s itchy, red skin. As dermatitis is often due to an underlying allergy to something in your pet’s environment, flea saliva protein, or food allergy, avoiding the triggers can help, but this is not always possible.
By keeping in close contact with your dog’s vet and following their recommendations you will likely be able to minimize the frequency and severity of your dog’s skin flare-ups. With seasonal or environmental allergies in dogs, much as for people with seasonal allergies, there is no cure. The goal is to keep dogs as comfortable as possible and avoid secondary skin infections as much as we can.
My dog’s skin isn’t getting better. When should I schedule a vet visit?
If your dog is experiencing any of the following symptoms, it’s time to schedule a vet visit:
- Scratching more than usual and seems uncomfortable.
- Licking, chewing, or scratching to a point where they are developing sores.
- Fur loss
- Head shaking
- Scratching at ears
- Lack of appetite
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