With the right shampoos or other topicals, patients can be bathed weekly or even daily. Photos courtesy Amelia G. White Itchy skin conditions are high on the list of problems pet owners bring to veterinarians. Approximately 10 percent of cats and dogs suffer from some type of allergy. Allergic dermatitis was the most common health issue last year among dogs insured with Nationwide, with more than 223,000 individual claims at an average cost of $293 per dog. In the same dataset, this condition ranked ninth for cats. Primarily, itchy skin occurs in response to one or a combination of hypersensitivity disorders: atopic dermatitis, food allergies, or flea allergy dermatitis. Parasites, infectious conditions, and other skin diseases can also be itchy. Fortunately for dogs and cats, flea infestation and flea allergy dermatitis are less common and not as severe these days, thanks to the number of effective flea control products on the market. However, atopic dermatitis and food allergies still frequently send pets into a frenzied itch-scratch cycle that is often followed by secondary bacterial and yeast infections. These patients may not simply have an itchy allergic hypersensitivity disorder, though. Atopic dogs and cats can have abnormal skin barriers, which are part of the atopic dermatitis syndrome. Skin barrier defects lead to moisture loss and make patients drier, scalier, and more prone to infections. A different approach Treatments for itchy skin haven’t changed, but the approach has. The rise of antimicrobial resistance over the last several decades has veterinarians taking a second look at how and when they use antibiotics. “We’re becoming much more judicious in our use of systemically administered antibiotics,” says Amelia G. White, DVM, DACVD, associate clinical professor of dermatology at Auburn University College of Veterinary Medicine. “We’re tending to use and lean more toward topical therapy as an approach to infections, both bacterial and fungal.” Abdominal self-induced hair loss and rash from environmental allergies in a domestic short-haired cat. Photo courtesy Wayne Rosenkrantz That may mean treating bacterial skin infections with medicated shampoos first. If that doesn’t work—or if the patient is immunocompromised and has a severe widespread skin infection—a systemic antibiotic may be used in addition to the topical therapy. Why topicals? While there are several good oral and injectable treatments to ease itchiness, topical treatments can play an important role in managing pruritic skin disease. Among them are moisturizing shampoos, as well as antibacterial, antifungal, and antiseborrheic shampoos. Additionally, topical therapies are available in numerous formulations, including crème rinses, sprays, mousses, lotions, and wipes, which makes finding one that will work for the pet an easy task. A number of factors come into play when deciding whether to treat topically or systemically. They include the following: size of the affected area; type and severity of infection; size, breed, and coat type of the affected animal; the patient’s overall health and how that might affect ease of bathing or speed of healing; and the pet owner’s ability and willingness to apply topical treatments as needed. Mild superficial or localized infections often respond well to topical therapies. A randomized, blinded, antibiotic-controlled study published in 2015 in Veterinary Dermatology found that cases of methicillin-susceptible and methicillin-resistant Staphylococcal infections responded to twice weekly bathing and daily treatment with a topical four percent chlorhexidine solution. Barrier defects may also be factors in the development and perpetuation of atopic dermatitis. Many patients with allergic dermatitis suffer from defects in the barrier function of the epidermis. Those defects lead to increased transepidermal water loss, causing skin to become very dry, Dr. White says. Itching and irritation follow. Skin barrier defects also contribute to an increased number of infectious organisms that overgrow on the skin and gain entrance on the more permeable skin surface, making infections more likely. When allergens and irritating substances find their way beneath the epidermis, patients develop more itching associated with their allergic dermatitis. Topical therapies are helpful in addressing itching caused by allergies, infections, and skin barrier defects. “There’s been a huge improvement in different types of topical products for pets with allergic disease, bacterial infections, and yeast infections,” says Wayne Rosenkrantz, DVM, DACVD, at Animal Dermatology Clinic in Tustin, Calif. “In an uncomplicated allergic patient without skin infections, we often use moisturizing shampoos that improve moisture content and barrier function of the skin. These products can also remove surface allergens that promote the allergic reaction.” Antibiotic-resistant infection on hock of a young hunting dog with allergies.Photos courtesy Amelia G. White These products often contain ingredients such as ceramides and phytosphingosine—popular in human skin care as well—and other moisturizing agents to keep skin hydrated and reduce irritation. Ceramides and phytosphingosine are lipids that are components of the skin barrier, along with cholesterol and fatty acids. When added to skin care products, they can help to strengthen the skin barrier, making it more difficult for irritants to invade; improve the skin’s ability to stay hydrated; prevent bacteria and yeast from overgrowing; and fight inflammation. Products such as colloidal oatmeal or oatmeal-based shampoos available without a prescription can also help to restore hydration and reduce skin inflammation. They probably won’t do much for severely atopic patients if they are the only thing being used, but they can be a good adjunct while determining what an animal needs to control an allergy long-term. For animals with Staphylococcal infections, products containing chlorhexidine are helpful. Often they are combined with anti-yeast agents for pets with yeast or Malassezia infections. Other antibacterial agents include ethyl lactate or lime sulfur. For a different type of itch, chlorhexidine and lime sulfur have some antifungal properties as well. Benzoyl peroxide is antibacterial, but it can be drying, so it should be avoided in patients with skin that is already dry and irritated. However, for patients with greasy or scaly hair coats, it can be a good choice. Salicylic acid is another antiseborrheic agent. Reducing resistance As a rule, topical therapy is preferred to systemic therapy because there are fewer issues with antimicrobial resistance, Dr. Rosenkrantz says. The ability to control a bacterial infection by more frequent bathing and other topical therapy is optimal. “Sometimes we have no choice, though, because the infections are not going to respond and we may have to select systemic antimicrobials, either based on cytology or culture and sensitivities,” he says. While topical therapy isn’t immune to resistance, it’s a less common issue compared to systemic use of antimicrobials. The same dog pictured previously six weeks later after being treated topically twice daily. Allergic animals with mild to moderate infections who are otherwise healthy can respond completely to topical therapy—but only with good owner compliance. When an infection is diagnosed, White recommends reaching first for a medicated shampoo instead of cephalexin or an antibiotic injection. Frequent bathing or other application of products is time-consuming, but when she explains the benefits for both pets and humans, owners see the value in topical therapy. For one, patients who receive antibiotic after antibiotic for skin infections may eventually no longer respond to the drugs. Reducing antibiotic use promotes human safety as well. While humans don’t typically become infected with the Staphylococcal bacteria that causes dog infections, which is called Staphylococcus pseudintermedius, they do get Staphylococcus aureus. And the bacteria between dogs and humans can share antibiotic resistance genes. For instance, if a client’s dog has a bad infection and is sleeping on the client’s bed and being petted frequently by the client, who then touches their own face or eats or drinks without practicing good hygiene, the client is intimately associated with that dog and their bacteria are intimately associated as well. If the dog’s bacteria are resistant because he’s been treated with antibiotic after antibiotic after antibiotic, they could teach the owner’s bacteria to become resistant, too. Down the road, if the owner needs antibiotics, they might not work for him. “Once you make them aware, they understand the value in the topical therapy and they’re going to be much more compliant because they don’t want to harm their pet unintentionally and they want to keep themselves and their family safe as well,” White says. Bathing benefits Besides being the vehicle for delivering medication and other substances, a bath has more basic benefits: it helps to reduce or remove allergens trapped on the skin’s surface and in the hair coat. It’s easy for environmental allergens to become entrapped in fur, then penetrate the skin and create inflammation. Washing them off may help to slightly reduce allergen exposure and bacterial and fungal numbers. But more important, perhaps, a cool or tepid bath feels good. Water itself is moisturizing, especially when combined with an emollient shampoo or rinse, but the temperature used is important. Cool water has a direct effect on reducing itchiness, in both animals and humans, but hot water promotes pruritus. Frequency of bathing can be important, too. Some clients may believe bathing too frequently dries out skin. Yet, with the right shampoos or other topicals, patients can be bathed weekly or even daily. “Most of our patients with an inflammatory skin disease, regardless of cause, usually can benefit from bathing at least once a week,” Rosenkrantz says. “We have had patients with resistant staph infections where we bathe them daily or every other day with chlorhexidine. In some cases, we’ve even used diluted bleach rinses and other topical disinfectants to follow up and control staphylococcal overgrowth.” Spray-on or leave-on mousses or rinses, as well as wipes containing chlorhexidine, can be applied in conjunction with baths or between baths. Things to consider Check for infection if an allergic animal who has been doing well flares. If not identified and treated early, infection can cause pets to become itchier. Keep the patient in mind. Cats typically don’t enjoy sprays or shampoos, but many will tolerate mousse or a wipe because it feels as if the owner is grooming them. Dogs are usually more amenable to topical applications, although some may be fearful about having their paws touched or dislike the hiss of a spray or mousse. And a spray may not effectively reach the skin of a dog with a thick, heavy coat. Take the client’s abilities into account when prescribing a treatment. Not every owner is able to hoist a large dog into a bathtub daily or even weekly. Some clients may not have the hand strength to pump spray bottles or open containers. Pets may have contact reactions to topical therapies. Ask clients to watch for and report such issues to you. Whether treatment is going well or poorly, the pet owner should tell you. If you know it’s not going well, you can recommend other topical approaches in a different formulation. Money is a factor. If a client isn’t able to properly apply the product or the pet resists the application, the treatment won’t be effective and clients will be out money they may not be able to afford. And finally, evaluate every case individually. No two cases are exactly the same. BREED PREDISPOSITIONS Genetics certainly plays a role in development of allergies, says Wayne Rosenkrantz, DVM, DACVD, at Animal Dermatology Clinic in Tustin, Calif. There’s direct and indirect evidence to suggest heredity is a factor, but environment contributes as well, he says. In dogs, breeds with heavy representation of allergies include all the terrier breeds, golden and Labrador retrievers, boxers, German shepherd dogs, Chinese shar-peis, Dalmatians, and bulldogs, to name a few. Cocker spaniels get allergies, but also their own subset of diseases such as seborrhea, which can lead to bacterial and yeast overgrowth. Another breed Dr. Rosenkrantz sees more frequently now for allergies is the French bulldog. “We’ve seen many, many Frenchies with atopic dermatitis, and they can be very difficult and refractory to therapy.” All breeds of cats can develop atopic dermatitis syndrome, Rosenkrantz says, with Abyssinians and Siamese seen in slightly higher numbers. Siamese and Siamese crosses also tend to be more predisposed to food allergies.
