Dog pruritus (intense itching)

The four main causes

• External parasites: fleas (still the leading cause of pruritus in dogs not on monthly parasiticides), ticks, sarcoptes (scabies, very pruritic), Cheyletiella, lice.
• Food allergies: reaction to a protein (chicken, beef, dairy, soy, eggs) or, more rarely, grains. Pruritus is non-seasonal, often paired with recurrent otitis and mild GI signs.
• Atopic dermatitis (environmental allergy): pollens, dust mites, mould, grasses. The most common allergy in dogs. Onset between 6 months and 3 years, often initially seasonal, then year after year with a longer season.
• Secondary bacterial or fungal infections: Staphylococcus and Malassezia overgrow on atopic or irritated skin. Pruritus increases, characteristic odour appears.

Seasonal or year-round?

Seasonal pruritus (spring-summer-autumn) suggests pollen or grass allergy. Pruritus worse in winter indoors raises suspicion for dust mites. Year-round pruritus without seasonal variation suggests food allergy, parasites, or advanced atopy with multiple sensitisations. Keep a short journal — a few sentences per week on itch intensity, walks, food changes — which helps the vet a lot.

Typical zones and what they suggest

• Ears (recurrent otitis): food allergy or atopy
• Paws (constant licking): atopy (grass mites, pollen)
• Tail base: fleas (flea-saliva allergic dermatitis — FAD)
• Armpits and groin: atopy
• Face, muzzle, eyes: food allergy
• Generalised, intense, contagious: sarcoptes (scabies)

RED FLAGS — see the vet promptly

• Open wounds, bleeding from scratching
• Lesions with pus or extensive crusts (pyoderma)
• Hair loss areas with thickened, blackened skin (chronic lichenification)
• Otitis with strong odour, black or yellowish discharge
• Scratching that prevents the dog from sleeping
• Swelling of muzzle, eyes or paws (acute allergic reaction)
• Multiple dogs or family members itching — scabies suspicion

What you can do at home

Check parasiticide — MUST be current (monthly for most products, every 3 months for long-acting like Bravecto). Regular flea-comb checks. Hypoallergenic or chlorhexidine-based shampoo baths if the vet has diagnosed secondary infection. Don't give human medications without vet approval — many are dangerous. For ears, DO NOT use cotton-tip swabs deep into the canal — they push wax further down.

At the vet

Clinical exam + skin scrape (looking for mites). Cytology with acetate tape or slides for bacteria and Malassezia. Possibly microbiology culture. For allergic suspicion, the elimination test (mono-protein diet with a protein the dog has never had — recommended Hill's z/d, Royal Canin Anallergenic, Purina HA — 8 strict weeks, no treats or scraps). For atopy, allergy testing (blood or intradermal). Chronic treatment: allergen immunotherapy, Apoquel or Cytopoint, short steroid courses in flares, antibiotics and antifungals for secondary infections.