Pruritus and Its Evaluation

Pruritus Overview

• Pruritus is itching, a sensation that provokes a desire to scratch.
• It is a common symptom in dermatological conditions.
• Other factors like anxiety, boredom, heat, or cold can worsen itching.

History Taking

• Important factors to consider include: seasonal versus non-seasonal itching, distribution of the itch, affected animals or people, duration of the problem, and successful treatments.
• A thorough history and physical exam are key for differential diagnoses.

Visual Analog Scale (VAS)

• Used to assess the intensity of pruritus.
• A scale ranging from 0 (no itch) to 10 (extreme itch), helps quantify the level of itch experienced by the animal.

Causes of Pruritus

• Allergic dermatitis is a potential cause.
• Parasites, infections, keratinization disorders, neoplasia, and autoimmune conditions may also cause itching.

Atopic Dermatitis

• Defined by the ACVD Task Force as a genetically predisposed, inflammatory, and pruritic allergic skin disease.
• Characterized by IgE reactions primarily directed against environmental allergens
• Multifactorial, encompassing genetic predisposition, defective skin barrier function, abnormal epidermal differentiation, and immunological abnormalities.
• Dogs show onset of symptoms between six months and three years of age. Symptoms can transition from being seasonal to non-seasonal. Older dogs may show symptoms after relocating to a warmer climate.
• Pruritus, with hairless areas (axillae, inguinal region, interdigital), can be generalized or localized.
• Clinical lesions often include erythema, lichenification, hyperpigmentation, and acral lick granulomas, along with secondary infections.

Cats

• Feline atopic syndrome (FAS) is a similar condition in cats.
• Diagnosis of atopic dermatitis or similar conditions is based on exclusion and history.

Feline Eosinophilic Complex

• Affecting skin, mucocutaneous junctions, and the oral cavity.

Feline Eosinophilic Granuloma

• Recognized in three forms: cutaneous, mucocutaneous, and oral.
• Frequently occurs simultaneously.

Feline Eosinophilic Plaque

• Lesions are identified as single or multiple, well-circumscribed, raised, erythematous, or ulcerated plaques
• Commonly found on the abdomen and medial thighs.
• Pruritus is typically severe.
• Secondary infections are common.

Rodent Ulcers

• Early lesions are usually crusted, erythematous, and depressed ulcers of the lip margin.
• Lesions may enlarge and develop red-brown pigmentation.
• Usually found on the upper lip, sometimes unilaterally or bilaterally.
• Can progress to squamous cell carcinoma.

Treatment

• Treatment for the eosinophilic granuloma complex requires identifying underlying causes, including hypersensitivity disorders.
• Antibiotics like amoxicillin clavulanate are often used.
• Other treatments might include prednisolone or cyclosporine.

Atopic Dermatitis Diagnosis

• A diagnosis is based on exclusion of other diseases and consideration of history and clinical signs.
• Allergy testing and biopsies are not conclusive for diagnosis.

Differential Diagnoses

• For dogs: food allergies, secondary infections, flea allergies, dermatophytosis, parasites.
• For cats: flea allergies, food allergies, dermatophytosis, parasites, and secondary infections.

Elimination Diet Trial

• The trial requires a complete diet change to an exclusive novel protein diet.
• All other treats and medications should be considered during the trial.
• A trial of 8-12 weeks could reveal the allergen.

Other Important Considerations

• Owners should always be mindful of the potential for secondary infections or parasites related to pruritus.
• In case of reoccurring problems or unexpected flare-ups, further evaluation is recommended.

Immunotherapy (ASIT)

• Allergen-specific immunotherapy.
• Long-term allergic control.

Important Considerations on Treatment and Diagnoses

• Avoid OTC diets.
• Evaluate the use of cyclosporine, a specific treatment for hypersensitivity reactions and itchiness, with caution and careful monitoring regarding potential side effects.
• Be aware of possible off-label therapies and related side effects.

Topical and Systemic Therapies

• Frequent bathing and topical therapies (such as chlorhexidine/miconazole shampoos, hypoallergenic shampoos, wipes) remove allergens, bacteria, and yeast in topical application.
• Systemic therapies, such as antihistamines, glucocorticosteroids, and other immune-modulating agents.