Signs of canine atopic dermatitis usually first appear between 6 months and 3 years of age. Initially there may be no visible lesions or just erythema.
The disease may start seasonally, but usually this progresses to non-seasonal disease, often with seasonal exacerbations. The clinical signs often increase and decrease in severity, depending on the level of exposure to allergens and the presence of secondary infections or concurrent allergic diseases.
Many of the signs that develop are due to secondary damage caused by self-trauma. Other lesions such as pustules, crusted papules and epidermal collarettes may develop due to secondary infections. Signs may also be exacerbated or altered by secondary factors such as the presence of fleas or infections.
The degree of pruritus is typically moderate (for example rated 5-7 out of 10). Secondary infections often increase the degree of pruritus and may make the pruritus poorly responsive to treatment for atopic dermatitis.
Typically lesions start at friction areas and skin folds:
- Face - around mouth, around eyes, inside the pinnae
- Feet
- Axillae
- Groin and perineum
- Flexural surfaces (front of elbows, front of hocks)
Some dogs present with only recurrent otitis externa.
In chronic cases the skin develops alopecia, excoriation, lichenification and hyperpigmentation.
