Contact Allergies. Fleas are a common source of contact allergies. Other common contact allergens include grasses, hay, plants, and trees. Toxins and chemicals (pesticides, carpet cleaners, etc.) provide additional potential sources for dog skin problems for both outdoor and indoor pets. For a dog that is seldom exposed to fleas, a single flea bite can inflame a dog's skin for several days.
Food Allergies are generally due to ingredients in your pet's food or treats. Symptoms of food allergies include itching and/or noticeable digestive trouble. A food allergy can be a reaction to almost any ingredient such as soy, wheat, yeast, or beef. Food allergies are so common that pet food manufacturers have invested millions of dollars in research, development and promotion of diets to help with food allergies in dogs.
Inhalant Allergies. With inhalants, pollen is the most common type of allergen, but cigarette smoke, air fresheners, smog, or other airborne pollutants can also be problematic.
Allergic Dermatitis (Dog skin problems caused by allergies)
Regardless of what causes the problem, this condition is common, it can last a lifetime, it is a challenge to diagnose, and once identified it can be resistant to attempts at treatment. Dogs with inhalant dermatitis will lick and chew at their paws and scratch their face, eyelids and ears. Others may erupt in hot spots or their skin may redden and be intensely itchy all over.
Sometimes there's a bad smell associated with allergic dermatitis called seborrhea, often the result of a secondary yeast (a type of fungus) infection. Seborrhea is a skin disorder in which the outer layers of the skin, the sebaceous glands, and the follicles are over-productive, leading to dull fur, dry flakiness, and smelly oiliness. This sebum, which becomes rancid, is the source of the odor. Frequent bathing, especially with a harsh shampoo, can irritate the skin and make this condition much worse.