Atopic dermatitis, caused by immune hyper-responsiveness, is wide spread in humans as well as in the dogs, especially in industrialized condition. Pet dogs are generally exposed to the same environment as their owners, and a significant portion of these animals are also known to suffer from this allergic disease. However, diagnosis and treatment methods of atopic dermatitis in animals have not been well established. We explored the possibility of using recently developed PG102 for the treatment of atopic dermatitis in the canine population. PG102 is a water soluble extract prepared from Actinidia arguta, and has been shown to produce significant therapeutic effect in variable allergy animal models. After oral administration of PG102 at a dose of 12.5 mg/kg daily for 4 weeks, severity of disease was greatly improved. IgE is one of representative members used to diagnose allergic diseases in humans. However, it is not well established whether there is any correlation between the serum level of IgE and atopic dermatitis. Our data indicated that dogs diagnosed to have atopic dermatitis contained higher level of serum IgE than the normal dogs and that treatment of dogs with PG102 significantly lowered the serum level of IgE. Taken together, this study demonstrated that PG102 treatment yielded significant amelioration of canine atopic dermatitis and down-regulation of serum IgE and that the serum level of IgE can be used as a convenient member for diagnosis of atopic dermatitis in dogs.