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→Clinical Signs
Signs are often, but not always, seasonal. Pruritus is the key feature of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions can include alopecia, erythema, scaling, crusting, excoriations and salivary staining. With time, lichenification, and hyperpigmentation develops. Certain areas of the body are affected more frequently than others: the feet, face, ears, axillae and vental abdomen are predilection sites. Secondary infections such as superficial staphylococcal pyoderma and Malassezia are common. A small number of cases may present only with chronic or recurrent otitis externa.
Signs are often, but not always, seasonal. Pruritus is the key feature of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions can include alopecia, erythema, scaling, crusting, excoriations and salivary staining. With time, lichenification, and hyperpigmentation develops. Certain areas of the body are affected more frequently than others: the feet, face, ears, axillae and vental abdomen are predilection sites. Secondary infections such as superficial staphylococcal pyoderma and Malassezia are common. A small number of cases may present only with chronic or recurrent otitis externa.
It makes sense that if the route of allergen contact is through percutaneous absorption, that hairless areas and areas of contact would be most commonly affected. A typical dog with atopic dermatitis will exhibit pruritus of the face (periocular and muzzle area), ears (pinnae and canals), feet, axillae and inguinal region. Dorsal pruritus is uncommon, and may in fact, if present be associated with flea allergic dermatitis which is often seen concurrent with atopic dermatitis.
Affected areas generally exhibit erythema, pruritus, and occasionally have a macular-papular eruption. With time, more chronic changes occur: lichenification, hyperpigmentation,, scaling and seborrhea. Secondary infections are common, with both bacterial pyoderma and malassezia dermatitis affecting the skin and yeast and bacterial otitis. Hyperhidrosis is a common symptom.
Some patients may exhibit symptoms of allergic rhinitis with sneezing, nasal discharge and allergic conjunctivitis. However, this is an uncommon manifestation of atopic disease in dogs.
In dogs pruritus is considered a hallmark of atopic dermatitis and emphasized by feet licking and nose or head rubbing. Since the occurrence of primary cutaneous lesions has never been firmly established, it may be that all the cutaneous changes are secondary to itch-induced scratching. This hypothesis is supported by the finding that although all of the dogs have signs of face rubbing and feet licking, only two-thirds have cutaneous lesions at the muzzle and pedal areas. In mild cases, one may only see broken hairs or salivary discoloration (rust colored) of the hairs. The incidence of a superficial pyoderma and of Malassezia infection is significantly higher in dogs with atopic signs together with immediate skin test reactivity, than in dogs with clinical manifestations but without a positive skin test. Otitis externa is a common finding in atopic dogs (up to 80 per cent) and even in 40 per cent of dogs as the initial problem. The head and legs are involved in 70 - 80%, and the axillaries, the abdomen and/or groins in 40 - 60% of dogs.
In dogs pruritus is considered a hallmark of atopic dermatitis and emphasized by feet licking and nose or head rubbing. Since the occurrence of primary cutaneous lesions has never been firmly established, it may be that all the cutaneous changes are secondary to itch-induced scratching. This hypothesis is supported by the finding that although all of the dogs have signs of face rubbing and feet licking, only two-thirds have cutaneous lesions at the muzzle and pedal areas. In mild cases, one may only see broken hairs or salivary discoloration (rust colored) of the hairs. The incidence of a superficial pyoderma and of Malassezia infection is significantly higher in dogs with atopic signs together with immediate skin test reactivity, than in dogs with clinical manifestations but without a positive skin test. Otitis externa is a common finding in atopic dogs (up to 80 per cent) and even in 40 per cent of dogs as the initial problem. The head and legs are involved in 70 - 80%, and the axillaries, the abdomen and/or groins in 40 - 60% of dogs.