Types

• According to Sniksnak.com there are five main types of dog allergies: inhalant, bacterial, flea, contact and food allergies. Inhalant allergies are the most common. While some dogs only have minor irritations from flea bites, other canines can have flea allergies so severe that a dog scratches or chews on itself. The least common dog allergies are contact allergies.
  
  

Symptoms

• There are several ways a dog can manifest an allergy, notes Sniksnak.com. Itching skin is the most common symptom, which can be either in one area (localized) or all over (generalized). Coughing, wheezing and sneezing are common respiratory signs of an allergy. Occasionally a dog may experience discharge from the nose or eyes. Signs of an allergy may also occur in a dog's digestive system, causing diarrhea or vomiting.
  
  

Misconception

• Although dog owners may think their pets are allergic to a particular food, it's not the actual dog food that causes allergies, it's one or more of the ingredients. According to k9web.com, some of the most common dog food ingredients causing allergies are beef, chicken, pork, whey, milk, egg, fish, wheat, soy, corn and preservatives.
  
  

Time Frame

• Some inhalant allergies aren't year-round, but only seasonal, notes the Dog Owner's Guide website. For example, a dog may inhale spring or grass pollen and then not exhibit allergic symptoms at other seasons of the year; ragweed pollen is a common irritant in late summer and early fall. Symptoms of this type of allergy involve a dog scratching, licking paws, shaking his head and rubbing his face on the ground to relieve the itching from swirling pollen grains in the air.
  
  

Consideration and Warning

• A young puppy or dog may not have an allergy, but can later develop one. As many dogs develop new allergies with age, Sniksnak.com recommends retesting a dog that was initially allergy-free about one to three years later in life.
  A dog can be allergic to even its own coat, cautions ShihtuGroomingHelp.com, especially if it has long or thick hair. A dog that swallows a lot of hair while cleaning itself can worsen the problem. Washing the dog every couple of weeks helps remove excess dander and hair, as does daily grooming using a stiff brush.