Types of allergy
An estimated 10 to 15% of dogs have some form of allergy. The most common type of allergy in dogs is atopic dermatitis: a type I or direct-type hypersensitive reaction to inhalation allergens, such as pollen and mites.
A flea allergy is a mixed allergy, a combination of direct-type I and delayed-type IV hypersensitivity, caused by contact with flea saliva. Food allergy where certain food components function as an allergen; contact allergy where the reaction is caused by antigens that come into contact with the skin (carpeting, blankets, shampoo and the like).
The clinical signs of different allergies mentioned above can look similar. However, the treatment of each of these allergies is quite different; this is why the correct diagnosis is important before starting the treatment.