The crusted cat: Scraping away the confusion
Two of the most important steps when you’re assessing dermatology issues in dogs and cats are (1) identifying primary and secondary skin lesions and (2) obtaining an accurate history. Most lesions are easily distinguishable from each other, but crusts and scales can be more of a challenge-especially when they occur on the same patient at the same time.
Dr. Melissa HallMelissa Hall, DVM, DACVD, shares her advice on how to tell the difference between the two, and how to zero in on accurate diagnosis and treatment of the most common causes of non-allergic crusting in cats.
One of these things is not like the other
First things first: Let’s talk about the difference between crust and scale.
Scale is an accumulation of loose fragments of the skin’s cornified cell layer. Scales can look like fine powder or large flakes, they can be greasy or dry, loose or adherent, and they can be various colors, such as white, brown or beige. Normal desquamation of the epidermis is invisible, so when larger flakes are apparent, abnormalities in keratinization or desquamation can be the underlying cause. Hall says most scaling disorders in cats result from chronic inflammation or poor grooming and therefore are usually a secondary manifestation.
A crust is an accumulation of dried exudate, serum, pus, blood or other cells, or scale that combines with other cellular debris to adhere to the skin surface. Crusts often become thickened in haired regions as hair and crust can mat and become tightly adherent. Crust can be variable in color-hemorrhagic crusts may be reddish, purulent crusts may take on a greenish or yellow hue, honey-colored crusts may be more infectious in nature, and crusts predominantly of keratinocytes and scale may be dark brown, silvery or black.
Crusts are often associated with inflammation, excoriation and pruritus, Hall says. They’re usually secondary types of lesions and may contain diagnostic clues such as infectious organisms, microbial elements or, if you’re lucky, dermatophyte hyphae. The diagnosis is often lurking in the crust, Hall says.
You’ve identified a crusty cat. Now what?
The first step, of course, is the same as in any other workup.
Get a history. How long has this been happening? Has it happened before? Is it seasonal? Are other cats, dogs or people in the household affected? Is the cat itchy?
Finding evidence of pruritus in the history may be difficult. Often an owner’s assessment is influenced by how much time they actually spend with the cat and how observant they are. We all know cats that are closet lickers.
To find evidence of pruritus, Hall advises looking at the shape of the crusts. Are they linear (see Photo 1)? Hall says that’s evidence of an itchy cat! Next obtain a trichogram. Pluck hairs from regions of thinning hair or alopecia and microscopically evaluate the ends for trauma. Tapered ends are normal. Broken and blunted follicular tips indicate that the hair has been sheared by overgrooming.
Photo 1. A cat with linear excoriations caused by infestation with the Notoedres cati mite. All photos courtesy of Dr. Melissa Hall.
Create a diagnostic plan. The diagnostic plan for cats with scales or crusting is consistent with a routine workup for most cases of feline dermatologic disease. It includes a physical exam, superficial and deep skin scraping, flea combing, direct cytologic impression smears, dermatophyte cultures, Wood’s light examination and histopathologic examination of the skin via skin biopsies. Additional tests based on baseline results can include immunohistochemistry, bloodwork and imaging studies.
For superficial skin scraping, Hall recommends applying the oil to the cat and then scraping. For a deep scraping, apply oil to the blade and then scrape until the skin bleeds-this is less messy than applying oil to the lesion. You can put both scrapings on the same slide. She doesn’t advocate squeezing the skin during a deep skin scraping: Demodex cati is very rare in cats.
Is your patient crusty but not itchy? Scrape anyway. Infectious mites may or may not cause pruritus.
Mites to suspect in crusty cats
Here are your chief suspects:
Notoedres cati. Scabies in cats is caused by Notoedres cati. Like other sarcoptic mites, these burrowers live in the epidermis and are obligate parasites; they live their entire life cycle on the host. Notoedres is highly contagious. Clinically, crusts develop initially on the face and medial proximal edge of the pinnae with subsequent secondary clinical signs that include erythema, scaling and pruritus (see Photo 2). The areas affected may spread to involve the rest of the body over time. Focus your superficial skin scrapings along the ear margins: Notoedres loves pinnae! These mites are generally much easier to find than their counterpart in the dog.
Photo 2. Lesions caused by the Notoedres cati mite.
Otodectes cynotis. These mites live predominantly in the ear canal and occasionally on the face, neck or body. Otodectes mites are also obligate parasites but are not particularly host-specific. They may affect dogs and small mammals in the environment as well. They cause disease both by direct mechanical irritation and by hypersensitive reactions. Classic clinical signs include young age of onset (although any age may be affected) with a typical black-brown ceruminous discharge that is usually bilateral.
These cats can be severely itchy, with erosions and significant crusting on the face and ears from excoriations. If the mite travels to another area of the body, lesions can mimic flea allergy dermatitis on the caudal dorsum. Chronic relapsing cases of otodectic mange are unlikely, and cats that have recurrent ear disease require an investigation into underlying allergic skin disease. These mites are also generally easily detected either by direct examination of the ear canal with an otoscope or in microscopic examination of direct smears of otic debris on a slide with mineral oil.
Demodex cati. Mange caused by Demodex cati is a relatively uncommon disease associated with the proliferation of these mites in the hair follicle or sebaceous glands, Hall says. The life cycle of this mite is similar to that of Demodex canis in dogs. Localized or generalized conditions can occur; however, the localized form in the cat is uncommon. Localized presentations are often limited to the head, eyelids and face or present as a ceruminous otitis externa (see Photo 3). These may be self-limiting or require topical, but rarely systemic, therapy.
Photo 3. Crusting on the chin caused by the Demodex cati mite.
The generalized form of the disease is more common, although it is still relatively rare. Burmese and Siamese cats are overrepresented. Clinical signs include alopecia, erythema, scale and crusting, and there may or may not be pruritus. Generalized disease is most often associated with underlying metabolic immunosuppression from such conditions as diabetes mellitus, hypercortisolism (either spontaneous or iatrogenic), malignant neoplasia or FeLV/FIV-positive status.
Demodex gatoi. This short-bodied Demodex mite lives in the epidermal pits of the stratum corneum as opposed to the hair follicles. Its life cycle is less understood; however, it is suspected to live its entire life in the superficial layers of the skin. Clinically this condition can present as anything from a nonpruritic case of alopecia and scale with crusting to an intensely pruritic case that has significant crusting with excoriations and trauma. The abdomen, lateral thorax and medial aspect of the legs are generally affected. These mites seem to be more common in southern U.S. states and areas of higher humidity.
D. gatoi mites are small and translucent and can be easily missed on skin scraping. Plus pruritic cats can easily remove them through grooming. Fecal flotation may be helpful in finding these mites in cases when skin scrapings are nondiagnostic. In addition, Hall recommends scraping along the margins of the areas of hair loss to increase the mite yield on superficial broad skin scraping.
Cheyletiella blakei. This mite is specific to feline patients, although on occasion other species of Cheyletiella (including C. yasguri and C. parasitovorax) can also infest cats. Often called “walking dandruff,” this condition is likely underdiagnosed and can be particularly problematic in catteries. The mites live on the skin surface and feed on cutaneous debris. They are more often diagnosed in young cats, but adults can be affected and are often asymptomatic. C. blakei presents a zoonotic concern as it can trigger a pruritic papular rash in people.
These mites are slightly larger than others and can be visualized as moving white spots in severely affected cats. Infestation will create significant scaling. Skin scraping or tape preparations can locate the mite.
Treatment for mites. If you see any mite, that’s considered conclusive-treat for that mite. If all tests come back negative, Hall considers the results inconclusive and treats empirically for mites with selamectin every two weeks for three applications. However, selamectin is ineffective for any Demodex species. In these cases the only treatment available is a lime sulphur dip every two weeks for three applications, Hall says.
Bacterial infection possibilities
Although most textbooks and references label superficial bacterial pyoderma or folliculitis as “uncommon” or “rare” in cats, most dermatologists and even recent literature disagree with this assessment. Superficial bacterial pyoderma is commonly undiagnosed and in many cases untreated in cats.
Crusted papular eruptions or miliary dermatitis are the most common presentations for folliculitis in cats; however, large areas of erythematous and erosive dermatosis can also be associated with large numbers of bacteria.
Pyoderma can be diagnosed with skin surface cytology: tape preps and direct impression smears of the affected area are indicated, and regular modified Wright’s stain is adequate. Eosinophils are often seen. Hall does not think culturing is necessary in routine cases; however, if rods are present or the patient is not responding to appropriate antimicrobial therapy, perform a culture.
Collect samples from the leading edge of the crust or collarette; swab under the crust and sample multiple sites. If the cat is on an antibiotic, do not stop the antibiotic before obtaining the sample. It’s also a good idea to perform cytology at the same time you collect your culture sample. If you see intracellular bacteria or bacteria with numerous inflammatory cells on cytology, you can assume that you are not dealing with normal flora. If you are concerned that the bacterial species present is resistant to the antibiotic, then the culture should not come back negative as there is active bacterial growth present.
While pyoderma is generally still considered a secondary complication of underlying disease, management of the bacterial component can be a critical factor in achieving control and remission of the primary disease.
Treatment is with empirical systemic therapies: amoxicillin-clavulanate, cephalexin, clindamycin and cefovecin are all good options. Treat for three to four weeks, and continue treatment for two weeks after resolution of clinical signs. If using cefovecin, administer two injections two weeks apart. Topical therapy with mupiricin cream is also an option because it is safe if ingested-i.e., licked off.
In cats, dermatophytosis is most often caused by Microsporum canis (see Photo 4). It’s common and can present in a myriad of ways. It can be characterized by either scale or crusting. Route of infection is contact with an arthrospore on an infected animal or in a contaminated environment.
Photo 4. A lesion caused by the dermatophyte Microsporum canis.
The most commonly affected animals are young, older or immunocompromised due to poor nutrition, ectoparasitic concerns or metabolic disease. Most healthy cats experience spontaneous remission, and treatment goals should be aimed at reducing environmental contamination and thus zoonotic potential.
Hall finds a trichogram to be a very helpful: dermatophytes like to hang out on the outside of the hair shaft, and irregularity or fuzziness on the hair shaft can indicate fungal spores. You may also get lucky and see haloed fungal spores or ghostlike hyphae (see Photo 5).
Photo 5. A dermatophyte visible on a trichogram.
A Wood’s lamp can help you determine where to take culture samples; some dermatophyte strains glow a bright apple-green color along the hair shaft. Scale and debris typically glow green-blue. By the way-Hall says it’s a myth that a Wood’s lamp needs five to 10 minutes to warm up. Delayed fluorescence is all a matter of perception and your eyes adjusting to the dark.
Recent evidence suggests that infected arthrospores can be found numerous centimeters away from the obvious clinical lesions. Because of this, most cases that don’t resolve spontaneously should be considered generalized and treated as such, Hall says.
Fungal culture is Hall’s diagnostic of choice, with dermatophyte test medium being the most reliable, inexpensive in-house method available. Dermatophytes consume the protein in the agar, creating alkaline metabolites that change the color to red. Dermatophyte cultures will grow in seven to 14 days. Color change noted after 21 days is usually due to contaminants, Hall says. She recommends incubating the samples at 82 degrees F, placing them next to a computer tower for warmth. Hall stores her cultures inside a plastic baggie with a moistened gauze square so the heat and humidity will encourage the fungus to grow. Check the samples daily for two weeks, then every other day for a total of 30 days.
“I check for 30 days just to make sure there isn’t something slow-growing,” Hall says. “It’s unlikely but it makes me feel more sure of the results.”
Dermatophyte colonies are white and fluffy; contaminant growth is usually darker, Hall says. You can use a piece of Scotch tape to lift the colony off the agar and place it on a microscope slide to identify. Hall recommends the website mycosesstudygroup.org as a resource with lots of pictures to help you identify dermatophyte species.
If you need a more rapid diagnosis, such as in households with higher zoonotic risk (pregnant women, children, immunocompromised individuals), Hall advises taking a biopsy of the leading edge of a lesion and requesting PSA or silver stain with the lab.
Treatment options for systemic therapy include the use of itraconazole, fluconazole or terbinafine as the drugs of choice. Because of the zoonotic potential of ringworm, Hall always starts oral antifungal therapy before culture results are back.
Coming up negative on your diagnostics for anything infectious and your paracitidal trial failed? Then you may be dealing with allergy, autoimmune disease or neoplasia. Further workup is required, including biopsy and allergy diagnostics, Hall says.
Dr. Sarah Wooten is a veterinary associate at Sheep’s Draw Animal Hospital in Greeley, Colorado. She contributes frequently to dvm360.com and also speaks at the CVC veterinary conferences.
Cats are notorious for scratching. Whether it’s using their back leg to scratch behind their ears, to showing off their kitty muscles on a scratching post, cats dedicate a decent portion of their time to itching, whether it’s themselves or a play toy. But there comes a point in time where your cat might cross the line between normal and obsessive.
In the latter case, there is a slight cause for concern. When cats itch their fur, especially concentrated in one area in particular, it is highly likely that your feline friend has dermatitis. As a skin condition, dermatitis is very uncomfortable and very demanding. It draws your cat in and captivates your kitten’s attention to the point where they don’t have time to live their lives and play with their catnip cotton mouse toys.
But how can something so seemingly insignificant as scratching become an actual problem? It seems impossible, but it happens more often than you might think. In fact, between six and fifteen percent of all cats have an encounter with dermatitis at some point in their lifetimes. Going back to the subject of cats going hand-in-hand with scratching, it’s not always obvious that a cat’s itching habit is a result of dermatitis. Our goal is to depict dermatitis so well that you will be able to spot the symptoms from a mile away. Let’s start out with a definition of dermatitis and go from there.
Dermatitis for Cats: What are the Symptoms of the Skin Condition?
While it’s important to understand dermatitis in entirety, it might be worthwhile to first determine if your cat’s behavior is in alignment with the common symptoms of feline miliary dermatitis before you worry about treating your cat for a skin condition. The most obvious indication of feline miliary dermatitis is a change in behavior relating to scratching, licking, and grooming.
So, let’s say your cat is itching like there is no tomorrow and you’re worried about the recent obsession with grooming their fur coat. The good news is that you can breathe because even if these behavioral changes are a result of feline miliary dermatitis, the skin condition is treatable. And the fact that you’ve caught on to your cat’s constant scratching is a great sign because it means you can get your kitty the attention they need.
But what if your cat has dermatitis and yet licking their fur is not a symptom they display in public? Cats are very secretive creatures, so there’s a high probability of your kitty hiding their behavior from you and licking their rash in private. Since this is a real possibility, we encourage you to look beyond the obvious side effect of itching and keep an eye out for all symptoms of cat dermatitis.
Aside from scratching, cats with dermatitis also…
- Have patches of fur missing as a result of hair loss
- Meow and purr more than usual
- Either want more attention or become more withdrawn
- Develop wet areas on their bodies where the dermatitis is most irritating
- Have areas of scabbed-over skin
- Be sensitive to petting
When it comes to pet health and ensuring that you are taking the appropriate steps to help your cat, the safest practice is to call your veterinarian rather than attempt to diagnose your cat on your own. Your vision might be clouded due to your emotional ties to your cat’s condition, and rather than letting unintentional bias cause you to make the wrong decision, always consult with a vet before taking any major steps in any direction.
What is Feline Dermatitis?
Dermatitis is defined as inflammation that starts on the surface of the skin, and as the condition worsens, it begins to affect inner layers of skin beneath the epidermis. Speaking of skin, there are two layers of skin that hold the most importance. The outermost layer of skin is called the epidermis and it is essentially the most protective layer. It acts as a barrier between the outside world and your internal organs.
As such, it is also the first part of your cat to experience the side effects of dermatitis. If cat dermatitis is treated and relieved early on, feline miliary dermatitis is less likely to expand and make its way to the dermis, which is your cat’s second major layer of skin. Located between the epidermis and the fatty tissues that lie beneath the skin, the dermis is where you would find sweat glands, lymph nodes, blood vessels, hair follicles, oil glands, and neurons.
All cases of cat dermatitis begin at the surface when an irritant starts to bother your cat’s epidermis. From there, your cat’s brain will receive signals from its body telling your little buddy to work on itching the problem area. Since one of the tell-tale signs of dermatitis is constant scratching, the feline miliary dermatitis will need to be addressed before the itchy aspect fades away completely. We’ll get into treatment methods for cat dermatitis soon, but before we talk about healing the problem, let’s discuss the three main sources of all feline dermatitis cases.
The Three Kinds of Feline Dermatitis
Dermatitis is an overarching term for a variety of skin conditions with varying levels of severity. The official terminology for dermatitis in cats is feline miliary dermatitis. While there are numerous different skin problems that cats face, they can all be placed into one of three main categories of cat dermatitis.
If you know which allergen caused your cat’s skin to become inflamed, then you’ll have an easier time figuring out which category of dermatitis your cat is experiencing. For cat dermatitis, there are about three main reasons behind the skin condition. In general, feline miliary dermatitis is a result of either a food allergy, an allergic reaction to something airborne, or fleas making a home in the hair follicles of your kitty cat.
Flea Allergy Dermatitis FAD
As you might have already assumed, flea allergy dermatitis, or FAD, is quite literally a skin condition caused by an allergy to fleas. When fleas bite your cat’s fur, they leave behind traces of their saliva. The experience of being bitten by a flea will result in dermatitis for cats with hypersensitivity to flea saliva. Though it seems like a minor detail, many cats do not take well to flea saliva. The result of the saliva of fleas sitting on your cat’s skin is irritation, which your cat will tend to by scratching, licking, and doing everything but leaving the area of skin alone.
Food Allergy Dermatitis
Many cases of feline miliary dermatitis are the result of an allergy to certain foods. As with all situations where allergies are involved, not all cats will be negatively impacted by the same things. A food item that is an allergen to one cat might be the best thing another cat has ever eaten. Food allergies are negative reactions to foods that your cat has no tolerance for, and unfortunately, you won’t always know that your cat is allergic to something until you give it to them and an allergic reaction unfolds.
As a general rule of thumb, cats should never eat.
- Seafood, including tuna
- Any foods that contain preservatives
When your kitty cat eats something that they are allergic to, their immune system will respond to an antigen and work to fight against the allergen. Whether your cat was born with an allergy or your feline friend develops an allergy over the years, always watch how your cat responds to any food that you give to him or her.
Just like humans, if cats are near a substance that they are allergic to, the act of simply rubbing against it or having an allergen in the vicinity can be enough to cause dermatitis in cats. Atopic dermatitis refers to instances where a cat comes into physical contact with an allergen. Another way of describing atopic dermatitis is to relate it to an allergic reaction. The distinguishing factor between atopic feline miliary dermatitis and allergic reactions is the prolonged time frame of dermatitis and the way that the allergen results in a rash.
Atopic dermatitis is an advanced stage of an allergic reaction on the skin. Allergies are genetic, so allergens vary from one cat to another. The fact that allergies are hereditary can be very helpful and insightful if you know the history of your cat’s parents. It’s always a good idea to keep an eye out for any allergies that your cat might have, but just because your kitty’s parents have certain allergies, it is not a definite certainty that your cat will develop the same allergies over time. It simply means they are at a higher risk of having allergies because their parents had them.
Another Way of Looking at Feline Miliary Dermatitis: Infectious vs Noninfectious
When you are working with something as vague as a skin condition, there is an incredibly high number of possibilities as to the cause of your cat’s dermatitis. While the three categories we talked about in the previous section are a great way of identifying all cases of dermatitis based on the primary cause of the condition, you can also look at feline miliary dermatitis through the lenses of being infectious or noninfectious.
Some specific causes of feline miliary dermatitis as a result of infection are.
- Ringworm and other instances involving fungi
- Cowpox, chickenpox, and other viruses
- Build-up of bacteria
- Flea bites
- Mites that burrow in your cat’s fur
Noninfectious causes of cat dermatitis include…
- Overexposure to sunlight resulting in a slight sunburn
- Squamous cell carcinoma
- Allergies to food
- Negative reactions of your cat’s nervous system
- Airborne allergies
- Feline eosinophilic granuloma complex
- Hypersensitivity to certain chemicals
- Adverse reactions to prescription medications
- Dermatitis as a result of a lack of grooming
- Liver disease
- Open wounds that don’t heal properly
- Urinary tract infections
Can Cats with Dermatitis Pass it Along to Other Cats?
A very reasonable concern about cats with feline miliary dermatitis is that the skin condition is contagious. Now, you don’t need to immediately quarantine your cat and deep clean every surface in close proximity to a cat with dermatitis. It’s rare for a cat to come down with a case of dermatitis that requires such drastic measures.
In order to figure out if your cat has a contagious bout of dermatitis, you will need to fill in one detail in particular. The first step is to determine if the origin of your cat’s dermatitis is an infection. If so, then your cat should be kept away from his or her feline buddies until the infection is taken care of and covered. Otherwise, your kitty cat is free to roam and interact with his or her animal friends.
What are the Treatment Options for Cats with Dermatitis?
Dermatitis for cats causes inflammation which, in turn, causes pain. As mentioned, it is imperative that you take your kitty cat to the veterinarian. While you’re at the vet’s office, your cat’s doctor will probably suggest one of the following methods of treatment for cat dermatitis.
- Flea shampoo
- Supplements for healthy skin
- Ointments intended to lessen inflammation
These are all suitable and well-researched ways of resolving symptoms of cat dermatitis, the only natural remedy for dermatitis on the list is the supplements. If your cat is in need of relief from dermatitis-related pain, and you want to explore a natural remedy for feline miliary dermatitis, then CBD is the answer to your prayers.
When cannabidiol is added to the equation, the severity of these two side effects of feline miliary dermatitis, in particular, are reduced. CBD works to minimize the inflammation caused by cat dermatitis, making symptoms more manageable.
What is Cannabidiol and Is it a Cat Dermatitis Home Remedy?
For the sake of securing your trust in CBD and ruling out any doubt you may have, let’s compare CBD and THC. The base-level knowledge that cannabidiol stems from the same, if not slightly different, source as tetrahydrocannabinol sometimes rubs cat owners the wrong way. That instinctive sense of hesitation is not surprising, particularly because THC is a source of psychoactive effects and, as all pet owners should know, you never ever want your animal to ingest anything of a psychotropic nature.
A common misconception about CBD is that it can cause you to get high, but this is very inaccurate, just as a principle. Cannabis has the potential to cause whomever or whatever ingests it to become high, but it is not cannabis as a whole that induces those mind-altering effects or physical reactions.
In fact, THC is responsible for these responses to cannabis, so if you have a cannabis plant or a hemp plant that contains little to no THC within its leaves, then the odds of getting high are greatly reduced, if not completely obliterated. The truth of the matter is that CBD oil for pets cannot get your pet high. Without a high concentration of THC, cannabidiol chemically does not contain the necessary compounds required for a psychoactive experience.
CBD for feline miliary dermatitis is the key to resolving cat dermatitis at home. All-natural home remedies for cat dermatitis are the way to go. One of the biggest perks of cannabidiol for cat dermatitis is that you can administer it to your kitty without having to step foot outside or wait in the vet’s office.
You’ll find a lot of comfort in CBD for dermatitis because the mere fact that you have the means to help your cat feel better is as good as it gets. When you have CBD in your household, your cat may never have to suffer from the pain of itching and scratching caused by dermatitis ever again. CBD is a kitty cat’s best friend.
Where to Purchase CBD to Help with Dermatitis for Cats
Innovet is the #1 pet health company to date. With CBD made from 100% hemp, and a quality control process that involves triple-checking the CBD sourced from Colorado, Innovet takes every measure possible to ensure that the CBD products on the e-commerce shelves are nothing shy of the best. After all, the best is what your cat deserves.
Sound impressive? Well, it gets even more incredible, because Innovet offers some of the highest quality CBD oils for cats with dermatitis. Need another reason to drop your jaw? Innovet ships CBD oils, CBD treats, Soft Hemp chews, snacks, and CBD creams to you!
There’s no need to take a trip to the store. Instead, place your order online and within a few days you can expect to open your front door to find a package from Innovet on your porch. If your cat could talk, he or she would ask you to buy CBD oil for feline miliary dermatitis. We’re sure of it. So what are you waiting for? Take a look at Innovet’s inventory today and buy CBD for your cat’s dermatitis. Your cat will thank you for relieving their inflammation and pain with an at-home dermatitis treatment from Innovet!