Scratching and itching are the most obvious signs of allergies in dogs.

The danger of letting this condition continue is that dogs will scratch furiously, often creating lesions in the skins, which provides the perfect conditions for serious staph infections and serious complications that require strong prescriptions and costly medical care. These infections will cause additional small red bumps called papules or little pimaple-like lesions called pustules.  Scabs can also form after the papules or pustules rupture. Finally, some dogs also develop chronic ear infections, runny nose, and diarrhea.

Dogs can develop secondary yeast infections and this is becoming increasingly common. Symptoms typically are greasy yellow scales that are odorous.  Yeast infections are often misdiagnosed but should be considered in any dog with these signs.

Many allergic dogs demonstrate seasonal allergy symptoms , and the itching increases during times when the specific allergens to which they are allergic are most prominent.  For example, pets with allergies to outdoors often begin showing allergic signs in the spring when the grass begins to grow after the winter.  Left untreated these allergies will develop into year round conditions as the pets immune system starts to break down over time. Some dogs with allergies have uncommon signs associated with allergies such as runny nose, runny eyes, asthma (wheezing) vomiting, and diarrhea. 

It is a safe bet to assume allergic atopic dermatitis if the dog is itching, but the skin appears normal.   The itchiness can be mild, moderate, or severe, but most allergic pets start off with moderate to light itching.  For a pet with sudden severe itching, it is more likely that fleas, or rarely seen food allergies are probably the diagnosis.

Left unattended, dogs will eventually develop chronic allergies withh pink or red skin, and bronzing and darkening of the skin.  The pinkish color is a sign of inflammation, and a reddish tint indicates more chronic inflammation.  The bronzing effect is due to pigment in the dog's saliva that discolors the skin.  In hyper chronic cases, the skin will also begin to darken as a result of the repeated scratching, licking, itching and inflammation.

Atopic dermatitis, also known as atopic eczema, is an atopic, hereditary, and non-contagious skin disease characterized by chronic inflammation of the skin. Many dogs with atopic dermatitis will also develop flea allergies and chronic bacterial infections. 

Chronic skin infections are so common in allergic dogs that every dog with chronic skin infections should be screened for atopy and also for underlying diseases such as hormonal disorders and a consultation with your vet is strongly suggested if the case has progressed along this far.