Changes

===Clinical Signs===

===Clinical Signs===

Signs are often, but not always, seasonal. Pruritus is the hallmark of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions commonly include alopecia, erythema, scaling, crusting, excoriations and salivary staining. Macular-papular eruptions are occasionally seen^beale. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption^beale, it follows that hairless regions are most frequently affected: the face, ears, axillae, feet and inguinal regions 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 hallmark of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions commonly include alopecia, erythema, scaling, crusting, excoriations and salivary staining. Macular-papular eruptions are occasionally seen^beale. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption^beale, it follows that hairless regions are most frequently affected: the face, ears, axillae, feet and inguinal regions are predilection sites. Secondary infections such as superficial staphylococcal pyoderma and ''Malassezia'' are common, and otitis externa often occurs concurrently. A small number of cases exhibit only chronic or recurrent otitis externa. Another uncommon presentation is allergic rhinitis, such as sneezing, nasal discharge or allergic conjunctivitis.

 

 

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.