Like people, dogs can suffer from allergies.

As in the human population, the incidence of allergies in pets seems to be increasing. While allergic
humans may often sneeze, wheeze or even have serious respiratory difficulties, allergic reactions in
pets are characterized by skin problems, exacerbated by their primary symptom—itching and
scratching. Cat and dog allergies fall into three main categories: flea allergy dermatitis, atopy, and
food allergy. Many pets can be affected by one or more allergy.


What is atopy and what are its symptoms?

Atopy is an allergic reaction to environmental substances like pollen, moulds, house dust mites and
animal dander (skin or hair fragments). It is most common in dogs, but some cats are also affected.
The incidence of atopy depends as much upon a pet’s genetic susceptibility as exposure to the
allergen itself. (An allergen is any agent causing the allergic reaction.) Terriers, Setters, Retrievers,
Dalmatians, Poodles, German Shepherds, Miniature Schnauzers and Chinese Shar-Pei are among
the breeds that are particularly prone to atopy.

Itching, mostly around the face, feet, lower chest and belly, is the primary symptom. Depending on the
cause, this may occur only seasonally (pollen) or year-round (moulds, dust mites and dander). “Hot
spots”, other skin infections and ear problems can develop. Frequent scratching due to chronic
irritation may lead to hair loss. Constant licking may also cause brown hair discolouration due to saliva
staining. While the onset of these signs can be seen from 4 months to 7 years of age they are typically
first noticed between 1–3 years of age.

How is atopy diagnosed?

Atopy is confirmed through a process of elimination. Other causes of itching, such as fleas, mites, lice,
bacterial and yeast infections, as well as food allergies, must be ruled out first. Your veterinarian will
ask you for a detailed history of your pet’s itching problem. Skin or serum (blood) testing for different
allergens may then be performed to help pinpoint the exact cause.

How is atopy treated?

Atopy is a lifelong condition and there is no known cure. However,
there are a number of ways to manage the problem:

  • Anti-itch therapy, including the use of drugs, medicated
    shampoos and conditioners.
  • Removing the source of the allergy from the environment as
    much as possible.
  • Hyposensitization uses a series of injections to gradually
    accustom your pet’s system to the allergen(s) causing the
    problem. Although its effectiveness varies, it provides at
    least some relief for around 75% of pets with atopy.

Flea Allergy Dermatitis

What is flea allergy dermatitis and what are its symptoms?

Flea allergy dermatitis (FAD), also called “flea bite hypersensitivity”, is a skin disease caused by an
allergic reaction to flea saliva. A single flea bite can trigger the disease’s intense itching. Dogs with
FAD chew and bite their backs, back legs, bellies or tails. FAD often leads to “hot spots”, or localized
skin infections. You may find fleas and flea dirt (the flea faeces look like black specks) on your pet,
although many cats and dogs with FAD have very few fleas, since they are constantly licking and

How is flea allergy dermatitis diagnosed?

Your veterinarian looks for the usual signs (scratching, skin sores, the presence of fleas and/or flea
dirt). He or she may also order an intradermal or skin test as FAD symptoms can resemble those of
other conditions, including external parasites (mites, lice), infections and other allergies, that cause
severe itching.

How is flea allergy dermatitis treated?

The best way to treat FAD is to prevent fleas from attacking your pet. Various insecticides and insect
growth regulators that eliminate flea infestations are available. Your veterinarian can recommend the
right product for your pet. Daily vacuuming and frequent washing of your pet’s bedding can also
reduce your home’s flea population.

To break the “itch-scratch” cycle that leads to skin infections, your veterinarian may prescribe steroids,
antihistamines and essential fatty acids to relieve irritation. Warm water baths and anti-itching
shampoos and conditioners also help.

What is most important to realise is that there is no cure for FAD: your pet will always be allergic to
flea bites and you must be continually on your guard to prevent further problems.

Food Allergy

What is food allergy and what are its symptoms?

Food allergy is an allergic reaction to one or more ingredients in a pet’s food. The most common
allergens are beef and milk products, cereals (wheat, corn, soya), chicken and eggs. The exact cause
of food allergy is not known. Perhaps a change in the pet’s immune system causes certain ingredients
to be perceived as “foreign,” initiating inflammatory mechanisms to fight off the perceived “intruder.”

The most common symptoms of food allergy are itching, licking or chewing. Otitis Externa (Ear
inflammation) along with other skin problems are also common in conjunction with food
hypersensitivity. Some pets may also have diarrhoea and other digestive problems. Symptoms can
appear at any age, whether a pet has just started a new diet or has been eating the same food for
several years.

How is food allergy diagnosed?

The only effective way of diagnosing a food
allergy is to put your pet on a
“hypoallergenic” or “exclusion” diet for a
minimum of 8–12 weeks. Such a diet
contains ingredients to which the animal has
not been exposed in the past. Because the
source of protein causes most allergic
reactions, exclusion diets use proteins—often
venison, fish or duck—that are normally not
found in regular pet food. An exclusion diet
may comprise home-prepared food or
prescription commercial hypoallergenic
products. Ask your veterinarian for their

If your pet has a food allergy, there should be a significant reduction in the symptoms after the
recommended period on the exclusion diet provided your pet is not also allergic to the newly
introduced ingredients. To identify all the food allergens, add a single protein for 1–2 weeks at a time,
while watching for a recurrence, or worsening, of symptoms. If this happens, remove the offending
ingredient from the diet. Consult your veterinarian for the correct procedure.

How is food allergy treated?

The best way to treat your pet’s food allergy is to carefully monitor his or her diet, in order to avoid
flare-ups. In rare cases, your veterinarian may also prescribe antihistamines and steroids.