Atopic Dermatitis + Skin Allergies in Dogs: Pictures, Causes + Solutions

Dermatitis refers to inflammation of the skin. Inflammation is the immune system's response to a threat (such as an allergen), which involves sending an army of different cells to an area of the body to fight the 'invaders' and fix the problem.

Why the Itch? Short Answer

Simply put, this influx of "helper" cells and their processes within the area create an itching sensation, which leads to the itching, scratching, redness, and self-inflicted skin trauma.

The Longer Answer, According to Research

To get more specific, these immune cells - T cells, dendritic cells, eosinophils, and mast cells - produce proteins such as:

1. Antibodies (immunoglobulins), which are proteins that identify and neutralize pathogens and foreign substances.
2. Cytokines, a substance secreted by immune cells to interact with other cells.
3. Interleukins, a type of cytokine, which are messenger proteins that help regulate immune and inflammatory response by communicating between different cells.
4. Enzymes, such as janus kinases (JAKs), which play a role in signaling cytokines.

Immunoglobulin (Ig)

Immunoglobulin, especially immunoglobulin E (IgE), determines what the body considers a harmful foreign substance - or in IgE's case, an allergen.

In dogs with canine atopic dermatitis (CAD), allergen-specific IgE can bind to other cells and "tell them" to produce substances that bring about inflammation and itch. High levels of IgE in the blood serum generally indicate an allergic reaction has occurred.

Interleukins (IL)

For dogs with CAD, a specific immune response signals an increased level of interleukin (IL). Interleukin has several forms, identified by number. Certain forms, including, IL-4, IL-13, and IL-31, play a direct role in activating itch-sensing neurons that call for - you guessed it - the itching sensation.

For reference, the treatment lokivetmab (commercially known as Cytopoint®) binds to IL-31 and neutralizes it, helping with overall itch in many dogs.

Janus Kinases (JAKs)

Like interleukins, JAK enzymes are involved in signaling between cells, though primarily in dealing with allergy. JAKs, like JAK1, can work to increase the activity of interleukins (i.e., more itch).

For reference, the treatment oclacitinib (commercially known as Apoquel®) inhibits JAK1, which affects the signaling of the interleukins IL-2, IL-4, IL-13, and IL-31, helping to reduce itch and inflammation.

How all of these cells, proteins, antibodies, and enzymes continue to be studied. For more on the pathogenesis of canine atopic dermatitis, see the article (also cited in Resources): Current Knowledge on Canine Atopic Dermatitis.

In general, some of the most common seasonal and environmental allergens (which account for the majority) behind dog skin allergies and canine atopic dermatitis are:

• Pollen, from trees, weeds, and grass
• Mold
• Dust mites
• Grass and hay
• Dander (dead skin) - which can even include human dander
• Flea saliva - (not very common, but results in a severe reaction called flea allergy dermatitis)

When it comes to dogs with food allergies, animal proteins are more common allergens than plant proteins:

• Beef (most common)
• Dairy products
• Chicken
• Lamb
• Eggs
• Pork
• Fish

Plant proteins:

• Wheat and wheat gluten (most common)
• Soy
• Rice
• Corn

For a (real) deep dive into canine food allergies, see our Complete Guide to Food Allergies in Dogs post.

Allergy tests (that work) come in two forms: a skin test called intradermal allergy testing (IDAT) and a blood test in the form of radio allergosorbic testing (RAST).

These tests are normally performed after a diagnosis of atopic dermatitis is made. It is recommended that neither should be performed unless you plan to start a hyposensitization treatment plan.

Tests that use saliva or hair currently have little evidence to support their validity and are not recommended by most vets.

Intradermal Allergy Testing

Intradermal allergy testing (IDAT) is only performed by veterinary dermatologists. IDAT involves sedating the dog, shaving a patch of hair along the side of the chest, and injecting a panel of various environmental allergens into a dog's skin. The sites are then observed after 15-30 minutes for signs of reactions and recorded.

Radio Allergosorbic Test (RAST) - Blood Test

These blood tests require a single sample that is drawn by a veterinarian, sent to a reference laboratory, and analyzed.

While RAST testing has a higher rate of false positives than IDAT, or positives that cannot be confirmed with IDAT, it is generally less expensive and less involved.

Final Considerations

Evidence suggests that 60-80% of dogs treated with allergen-specific immunotherapy (hyposensitization) based on RAST or IDAT results experience a significant improvement in their condition.

However, these tests are not to be used in testing for food allergies, as the results are inconclusive.

The only truly accepted test for food allergies in dogs is an food elimination trial. Currently, there are no hair, saliva, skin, or blood tests that yield conclusive results.

A food elimination trial involves strictly feeding your dog a specific hypoallergenic diet for 8 to 12 weeks. Such a period of time will allow time for the immune system to decide if it "likes" the new food or not.

During the trial, owners must only feed the prescribed diet; even treats and flavored medications or supplements should be avoided. These diets feature a single protein source that is either hydrolyzed or novel (new) to the dog.

After the 8 to 12 week trial period is up, the dog's previous food is given to them for a week to see if the allergy flares back up.

Because the immune system has already established a "dislike" for that food, the symptoms should reappear within the week - sometimes even within hours.

At the first sign of symptoms, the old food is verified as "bad juju" and discontinued.

See our Complete Guide to Food Allergies in Dogs post for a full plate of info.

Allergy shots (also called allergy immunotherapy) essentially retrain your dog's immune system by exposing them to small amounts of allergens. This amount is slowly increased over time until the body builds a tolerance to it.

Per vety.com, these shots cost between $1,000 and $4,000 per year, not including allergy testing costs (see below).

More Quick Info on Allergy Shots for Dogs

Before the shots, a vet or veterinary dermatologist will perform a blood test or intradermal skin testing to determine what environmental allergens your dog is sensitive to.

Depending upon the clinic and location, intradermal testing or a blood test can cost between $200 and $400. This does not include the initial vet exam fee.

The cost range of $1,000 to $4,000 per year for allergy shots can rely upon whether you give the injections at home or having them done in clinic. Injections given at-home will land toward the lower end, while injections given in-clinic will be higher.

The shots are given in two phases: the buildup phase and the maintenance phase. The buildup phase requires once- to twice- per week injections for several months. This phase can be more expensive.

After the buildup phase, the maintenance phase reduces the frequency of injections to every 2 to 4 weeks and lasts 3 to 5 years.

While expensive, it is reported that 60 to 80% of dogs with environmental allergies benefit from allergy immunotherapy treatment.

Research seems to indicate that this is true. Many clinical researchers now accept "living mostly indoors" as one of the criteria for diagnosing atopy.

Why Do Indoor Dogs Get Atopic Dermatitis More Often? The Short Answer

Dogs that live or have lived inside for most of their lives will generally have a more limited exposure to allergens, which does not permit their immune system to build a defense against them - especially at a young age.

This means that indoor dogs' immune systems are typically less prepared for, and more overreactive to, environmental allergens than outdoor dogs.

Why Do Indoor Dogs Get Skin Allergies More Often? The Longer Answer

All in all, atopic dermatitis and skin allergies are the product of a complex amalgamation of genetic and environmental factors.

Environmental factors play a major role in the development of a young dog's immune system, and canine atopic dermatitis (i.e. skin allergies) is more frequently associated with living in an urban environment and living primarily indoors than a rural or outdoor environment.

Exposure to a diverse spectrum of microbes early in life stimulates the young immune system, forcing it to adapt and develop the appropriate inflammatory response.

On top of this, higher societal standards of hygiene in the living space further decrease the number of microbes that an individual is exposed to. This not only holds weight with dogs, but humans as well, as the prevalence of atopic dermatitis in humans worldwide has increased dramatically in the past half century.

On the flip side, various studies have found these factors to help protect dogs against developing atopy:

• Born and live in a rural environment
• Live outdoors
• Live within the household they were born in
• Regularly walk through woodlands, fields, and/or beaches (i.e. non-urban sites)
• Have regular contact with other animals
• Live within a family of more than 2 children

These factors do not prove causality nor apply in all cases, but they offer an interesting insight into how the living environment plays a role.

See the article (also cited in Resources) Current Knowledge on Canine Atopic Dermatitis for more info.

A few things to consider with stubborn atopic dermatitis and rashes on dogs that stem from allergies:

1. Infection may be present.

Bacterial infections (pyoderma) and yeast infections (Malassezia) are very common in dogs that get skin allergies and atopic dermatitis.

These infections can get established quickly, become compound (multiple bacteria and/or fungi), and take time - and possibly different medications - to eradicate completely. Established and compound infections can require weeks or months to eradicate.

2. Managing allergies, or treating the symptoms?

Dog skin allergies and atopic dermatitis usually take more than rubbing a cream or bathing with special shampoo to get rid of the underlying problem.

Topicals - yes, even ours - can help relieve the area and heal the skin, but if the dog remains exposed to an allergen to which he/she is sensitive, you may be only mitigating the symptoms and not solving the problem.

If an allergen is unavoidable, regular systemic medication or allergen-specific immunotherapy may be necessary to get the immune system's response in check.

3. Possible food allergy

Food allergies aren't always immediately apparent. In fact, they take time to develop. A dog can eat the same food for months or years before an allergy begins to appear.

See our Complete Guide to Food Allergies in Dogs post for a full bowl of info.

4. Possible hormonal disorder, autoimmune condition, or cancer instead of allergies

Though uncommon, there are some hormonal disorders (e.g., hypothyroidism and Cushing's disease), autoimmune disorders (lupus erythematosus, for one), and certain cancers that can exhibit abnormalities or manifest as a rash or lesions.

Atopy is caused by an allergic reaction triggered by the immune system, while mange is caused by parasitic mites.

Both of these skin conditions can exhibit extreme itching, redness, rash, and fur loss, and many people get the two confused.

Mange comes in two forms - one for each species of mite that causes it - demodectic and sarcoptic mange.

Demodectic mange (also called demodex, red mange, or demodicosis) is more common. Demodex mange mites live on and consume hair follicle material. An overgrowth leads to the spreading fur loss and itching. This form tends to affect puppies, senior dogs, and dogs with compromised immune systems.

Sarcoptic mange (scabies) is less common, but it is spread from host to host and can affect any dog. Scabies consume dead skin and hair, burrow into the skin to lay eggs, and are EXTREMELY itchy.

The spread of the mites and the trauma from scratching create fur loss, lesions, sores, and infections. Scabies can be fatal if left untreated.

See our Mange in Dogs Resource for much more info.

Ringworm is caused by a fungus (not a parasite), while atopy is simply an allergic reaction.

Ringworm attaches to skin, nails, and hair and feeds on dead skin and hair follicles, spreading as it multiplies.

In humans (yes, it can be spread to other species, including us), ringworm takes on a circular, red spot. In dogs, it can:

1. Appear as round patches of fur loss with a reddish ring around the edge.
2. Appear as an amorphous, spreading patch of hair loss. Hair within ringworm lesions is typically very brittle.
3. Affect the nails, making them brittle.

In addition, ringworm is incredibly hardy and can live on abiotic surfaces such as carpet, wood, bedding, brushes, food bowls, etc. for over a year.

Unfortunately, dealing with ringworm means not only isolating your dog, but doing thorough decontamination work on everything they've come into contact with.

See our Ringworm in Dogs Resource for much more info.

Research says that it's even. Atopic dermatitis affects both genders equally.

No, atopic dermatitis is neither contagious to other dogs or other animals.