As weird as it may sound, the whole concept of allergies is relatively new. Before the 20th century, allergic reactions were scarcely known or recognized. In fact, the term ,,allergy’’ was coined in 1906, by a Viennese pediatrician, Baron Clemens von Pirquet.However, today, over 10% of the population suffers from allergies. As the incidence of allergies has increased in people, there has been a similar increase in allergies in dogs.An allergy can be defined as a state of over-reactivity or hypersensitivity of the immune system to a particular substance. The substances that hold the power to trigger such reactions of the immune system are called allergens. The symptoms of allergies differ, depending on the place where the allergic reaction occurs:
  • The dog’s skin – localized or generalized itchiness and skin inflammation or irritation
  • The lining of the airways – coughing, sneezing, wheezing and discharge from the nose and eyes.
  • The lining of the gastrointestinal tract – vomiting and diarrhea.
  1. Skin allergies
Skin allergies are the most common type of allergies in dogs. According to some classification, food allergies and environmental allergies are also classified in skin allergies. However, the most common skin allergy in dogs is the flea allergy dermatitis (FAD). Flea allergy dermatitis is caused by the dog’s sensitivity to the fleas’ saliva.The best way to address this issue is by removing the fleas and bathing the dog in soothing, hypoallergenic shampoos.The biggest issue with skin allergies is that they increase the risk of secondary infections. Simply stated, as the dog scratches, licks and bites its skin, it makes it more vulnerable to yeast and bacteria.
  1. Contact allergies
Contact allergies, also known as allergic contact dermatitis are the least common type of allergies in dogs. In contact allergies, the allergic reaction occurs only on parts of the body that are in direct contact with the allergen. For example, grass sap causes skin inflammation on the relatively hairless underside of the dog’s body.Allergens that may cause allergic contact dermatitis are:
  • Pyrethrins found in flea collars
  • Pesticide used on lawns
  • Certain types of grasses
  • Certain types of materials, such as wool and synthetic.
The treatment requires identifying the allergen and then eliminating it. Depending on the allergen, in some cases it is advised to bathe the dog with hypoallergenic shampoos.It should be noted, that some cases of atopy, may have food allergy as a component or be triggered by a certain type of food.
  1. Atopy
Atopy is a special type of allergy, usually defined as relapsing inflammatory skin disease caused by complex interactions between genetic predispositions and environmental factors. Dogs with atopy have impaired skin barrier that leads to defective permeability and enhanced penetration of environmental allergens. The condition may be:
  • Seasonal
  • Non-seasonal.
It should be noted that the most commonly observed sign in dogs suffering from atopy are:
  • Licking/biting of the paws (usually associated with non-seasonal atopy)
  • Licking/biting of the flanks (usually associated with seasonal atopy)
Because of its complexity, treating atopy requires:
  • Anti-inflammatory drugs – antihistamines and corticosteroids
  • Shampoos – to sooth the irritated skin and rinse out the allergens from the coat.
  • Hyposensitization – to reprogram the dog’s immune system.
  1. Human food allergies
Food allergies can develop to almost any protein or carbohydrate from the food. The most common causes of food allergies are:
  • Beef
  • Dairy
  • Chicken
  • Lamb
  • Soy
  • Wheat gluten.
Treating food allergies requires performing a two-phased trial:
  • Elimination
  • Challenge
During the elimination phase, a new diet is carefully selected to try to eliminate any foods containing dietary proteins thought to be responsible for the food allergy. During the second, challenge phase, the dog needs to be monitored for a return of clinical signs upon dietary challenge. For example, if the dog’s symptoms subsided on a diet of rabbit and potatoes, then you could add beef to the diet for 2 weeks. If there is no recurrence of signs, the next component can be added. The next component can be chicken. If the dog began to show symptoms while fed with chicken, then it could be assumed that chicken was one of the things he was allergic to. After the symptoms of the allergenic chicken have subsided, another component can be introduced. This strategy should be continued until all of the offending ingredients are identified or at least until a well-balanced acceptable diet is achieved without any recurrence of food allergy
  1. Dog food allergies
As weird as it may sound, dogs can be allergic to dog food. The reason for that may be one specific ingredient or multiple ingredients. It is also possible for the dog not to be allergic to the food’s ingredients, but to contaminants found in the food or substances used during the food’s manufacturing.Dog food allergies can occur no matter which food brand you use. Never assume that there is something wrong with the food. The food allergy is a unique immune response.The treatment for dog food allergies is the same as in human food allergies.
  1. Acute allergic reactions
Acute allergic reactions are the most alarming type of allergy in dogs. Fortunately they are not very common. However, it should be noted, that if the dog’s reaction to the allergen is severe enough, it can go in an anaphylactic shock. As in humans, anaphylactic shocks in dogs, if not properly treated can be fatal.The most common causes of acute allergic reactions in dogs are:
  • Insect bites and stings (usually bee stings)
  • Certain vaccines
  • Certain drugs and medications.
Depending on the severity of the case, some dogs will need antihistamine therapy, while others may require full anti-shock treatment.
  1. Environmental allergies
Dogs can be allergic to a plethora of irritants from the environment. These allergens can be categorized as:
  • Outdoor allergens – ragweed, grasses and pollens
  • Indoor allergens – molds, dust mites, cleaning chemicals, certain fabrics, cigarette smoke.
By selective breeding, humans have increased the genetic predisposition to allergies in some dogs, and by altering their natural environment we have also increased dog’s exposure to potential allergens. Some of these allergens affect the skin, while others affect the respiratory system.Depending on the duration of the clinical signs, environmental allergies can be classified as:
  • Seasonal (usually associated with indoor allergens)
  • Non-seasonal (usually associated with outdoor allergens)
The ideal treatment option is elimination of the allergen. If that is not possible, the dog should receive oral antihistamines or corticosteroids, prescribed by a licensed veterinarian. 
  1. Allergies to medicated shampoos
It is not uncommon for dogs to have allergic reactions to medicated shampoos. Adverse shampoo reactions usually happen shortly after exposure and tend to increase in intensity as the dog’s exposure increases. They usually manifest with hives and itching.If your dog shows signs of allergy, first of all, rinse the areas that came into contact with the shampoo. Then, if needed your veterinarian may prescribe a suitable topical and oral therapy. In conclusion, if you are find your dog shows any of the mentioned symptoms, it would be best to consult with a veterinarian or a pet nutritionist. With timely and proper treatment, your dog should recover to the old-self in no time!