Top 3 Causes of Pruritic Skin Diseases in Dogs

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Skin issues are a frequent reason for veterinary visits, with 1 study reporting >1 in 5 small animal visits involve pets with dermatologic conditions.¹ Pruritus, a common and often frustrating manifestation of skin disease, is the most common presenting complaint in dogs with dermatologic disease.²

Identifying the underlying cause of pruritus is essential for guiding treatment. In many cases, that means first ruling out infection and parasites through physical examination and common diagnostics tests such as skin cytology and skin scrapes. When initial diagnostics are inconclusive, other differentials should be considered and other diagnostics pursued, including trichograms, dermatophyte cultures, hypoallergenic food trials, intradermal allergy testing, and/or skin biopsies.

Below are 3 underlying causes to consider in pruritic dogs.

1. Allergic Dermatitis

Allergic dermatitis, a top cause of pruritic disease in dogs, can be further categorized based on the inciting allergen. The most common causes include flea bite hypersensitivity, atopic dermatitis, and food-allergic dermatitis.³ Physical examination, patient history, and allergy testing can all be used to delineate the underlying cause and determine treatment.

Managing pruritus, both in the short- and long-term, is critical for maintaining both the pet and pet owner’s quality of life.³ Antipruritic agents such as Apoquel® (oclacitinib tablet), Apoquel® Chewable (oclacitinib chewable tablet), or Cytopoint® should be considered to manage allergic pruritus. Apoquel® does not interfere with intradermal allergy testing, can be used concurrently with allergen immunotherapy, and can provide antipruritic effects starting within 4 hours of administration.^4-6 Cytopoint can provide relief within 24 hours and can control allergic pruritus for 4 to 8 weeks with a single injection, making it an excellent option for long-term management of pruritus associated with allergic and atopic dermatitis in dogs.⁷

2. Ectoparasitic Infestations

Ectoparasitic infestations, including fleas, contagious acariases (eg, Sarcoptes spp, Otodectes spp, Cheyletiella spp), and pediculosis, can cause intense pruritus.^8-11

Ctenocephalides felis is the most common ectoparasite of dogs in North America and can cause intense pruritus, even in the absence of a flea allergy.¹² Aside from a history of pruritus and visible fleas, clinical signs of flea infestation include erythemic bites, alopecia (especially on the dorsal lumbosacral region), presence of flea dirt, and, most severely, iron-deficiency anemia, especially in puppies.^12,13 These signs are most common in flea-allergic patients, with nonallergic patients showing variable degrees of pruritus.

Sarcoptic mange caused by Sarcoptes scabiei is a common, contagious pruritic parasite in dogs and has zoonotic potential.⁹ This intensely pruritic condition can lead to hyperkeratosis, alopecia, and, in some cases, self-mutilation.⁹ The most commonly affected areas include the ear margins, lateral elbows, and lateral hocks, although the entire body can be affected.⁹ Diagnosis is established with identification of mites on skin scrape; however, false-negative results are common.⁹ Treatment for scabies should be considered in the face of a negative skin scrape if clinical suspicion remains high. In addition to parasiticides, antipruritic drugs like oclacitinib may provide rapid relief and reduced pruritus.¹⁴

Although more common in cats, Otodectes sppmites may inhabit the ear canal of dogs, causing a pruritic response.¹⁰ Signs of the presence of Otodectes spp mites include headshaking, scratching at the ears, erythemic ear canals, and accumulation of dark, otic debris, with mites being identified on ear cytology.

3. Secondary Infections: Pyoderma and Malassezia Dermatitis

Bacterial and yeast infections often develop secondary to other conditions (eg, allergic dermatitis, endocrinopathies) and can be a significant cause of pruritus. Commonly, pyoderma manifests as papules, pustules, alopecia, crusts, and/or epidermal collarettes. In cases of Malassezia spp infection, signs may include intense pruritus, a foul odor, lichenification, and/or hyperpigmentation of the skin. Commonly affected areas of secondary infection include the ears ventral neck, ventrum, medial thighs, paws, and muzzle.^15,16

Skin cytology is used for diagnosis and is critical in differentiating bacterial infection from Malassezia spp infection. Culture and susceptibility testing is encouraged in patients with recurring pyoderma or those that fail to respond to appropriate topical or systemic antimicrobial therapy.¹⁵ Veterinary professionals should consider the threat of rising antimicrobial resistance when prescribing systemic antibiotics for staphylococcal pyoderma, and topical therapy is recommended as the first-line choice of treatment.¹⁵

Conclusion

Pruritus in dogs can arise from a wide range of underlying causes. By identifying the root cause of the patient’s clinical signs, veterinarians can develop a targeted management plan tailored to the individual.

Therapies such as Apoquel and Cytopoint can provide fast relief from allergic itch, help restore patient comfort, and help improve quality of life for both patients and their owners. With the right tools and a thoughtful, informed approach to pruritus, veterinarians can make a meaningful impact on the well-being of their itchy patients—and the people who love them.

APOQUEL & APOQUEL CHEWABLE IMPORTANT SAFETY INFORMATION

Do not use Apoquel or Apoquel Chewable in dogs less than 12 months of age or those with serious infections. Apoquel and Apoquel Chewable may increase the chances of developing serious infections, and may cause existing parasitic skin infestations or pre-existing cancers to get worse. Consider the risks and benefits of treatment in dogs with a history of recurrence of these conditions. New neoplastic conditions (benign and malignant) were observed in clinical studies and post-approval. Apoquel and Apoquel Chewable have not been tested in dogs receiving some medications including some commonly used to treat skin conditions such as corticosteroids and cyclosporines. Do not use in breeding, pregnant, or lactating dogs. Most common side effects are vomiting and diarrhea. Apoquel and Apoquel Chewable have been used safely with many common medications including parasiticides, antibiotics and vaccines. See full Prescribing Information at ApoquelPI.com and ApoquelChewablePI.com.

CYTOPOINT INDICATIONS

Cytopoint has been shown to be effective for the treatment of dogs against allergic dermatitis and atopic dermatitis.