Human allergy season reaches its zenith in spring, when hay fever strikes. In some locations, such as Davis, California (home to my veterinary school), allergens reach phenomenal levels and hay fever reaches epidemic proportions.

Owners often suspect allergies when their dogs have red, itchy, watery eyes. At first glance it seems reasonable that dog allergies might manifest in the same way, and in the same season, as our own. But it turns out that allergic conjunctivitis (conjunctivitis is a fancy way of saying eye irritation) is not as common in our canine companions as many people suspect. There are many other conditions, especially infectious conjunctivitis, that are more likely to cause eye issues in dogs.

Although allergies are not a terribly common cause of eye problems in dogs, I am sad to say that large numbers of dogs do suffer from allergies. Canine allergies manifest most commonly as skin problems. And, according to data from Trupanion pet insurance, they peak in July, August, and September.

Itchy skin is the most common symptom of canine allergies. The ears also may become itchy. Both the skin and the ears can become infected with opportunistic bacteria and yeast as a result of irritation that develops when allergies strike. Allergies may cause rashes or scabs to form, and allergies combined with infection may cause the skin to thicken and become red, bald, and malodorous.

The most commonly affected areas of the skin include the armpits, the groin, the base of the tail, the tops of the feet, and the sides of the muzzle.

Dogs with allergies, like humans with allergies, suffer tremendously.

The most common causes of allergies in dogs

So, what are the most common causes of allergies in dogs? Allergies are caused by proteins called allergens. The most serious and common allergens, by a mile, are produced by fleas.

I can read your mind. You are thinking, “But my dog doesn’t have fleas.” If I had a nickel for every time I’ve heard that one, I could (and would) buy a ticket to Tahiti. This brings me to what I call the “paradox of fleas.” Dogs who have fleas almost never are allergic. Dogs who are allergic almost never have fleas.

Fleas themselves do not cause allergic reactions. Their bites, and more specifically allergenic proteins in their saliva, are what trigger allergic reactions. Allergic dogs don’t tend to tolerate fleas, and unless they are debilitated they groom the pests off efficiently (and therefore rarely have fleas). But a sensitive dog will develop skin problems even if he is bitten only now and then by wandering fleas.

Flea season, in the northern hemisphere, peaks in the summer. I therefore am not surprised that Trupanion’s data show that allergies peak when flea activity peaks.

Other common causes of allergies in dogs include proteins in food (beef is the No. 1 food allergen), and environmental allergens such as pollen, cockroach feces, dust mites, and even human dander.

How to deal with canine allergies

Many people wonder whether they should purchase over-the-counter antihistamines to treat their dogs’ allergies. The short answer is no. It is not only illegal to administer over-the-counter medications to dogs, but such medications also rarely are effective.

Allergen avoidance is the best way to address allergies in dogs. Since fleas are the No. 1 source of allergens in dogs, high-quality flea prevention is the most effective way to prevent canine allergies. I know this first hand. My pal Buster suffered redness and itching in his groin and around the base of his tail two Augusts in a row. I switched him from Frontline Plus to Comfortis (a newer product), and for the last two years Buster has not suffered from August itchiness. Note that although Buster is allergic to fleas, I have never seen a flea on his body or in the house.

Food allergies can be addressed through so-called elimination diets. These diets contain limited ingredients, and they may be less allergenic than regular foods. Such diets used to be available only through veterinarians, but a host of high-quality new products are available at specialty pet stores.

Environmental allergens such as pollen can most readily be avoided by cleansing the skin after walks. The feet, which are especially prone to itching due to allergies, can be cleansed with a moist wash cloth. Dietary supplementation with omega-3 fatty acids (fish oil) may help to make the skin resistant to the effects of allergens.

If allergen avoidance is not enough

Many unfortunate dogs still suffer from skin problems despite diligent allergen avoidance by their owners. Such dogs may benefit from regular oatmeal (yes, that type of oatmeal, made into a commercial shampoo) baths. Hyposensitization injections, also known as allergy shots, can be prepared for dogs based upon results of blood or skin allergy testing.

Finally, medications may be necessary to treat allergies in severely affected individuals. Oral antihistamines aren’t effective in many cases. However, other medications, especially topical or oral steroids, can often help bring the itching under control. Antibiotics and antifungal medications may be used to treat secondary skin infections. Medications (especially steroids) have the potential to cause side effects, so I recommend avoiding them if possible. Sadly, some dogs cannot be made comfortable without them.

Read more about allergies and flea control on Dogster: 

• What Options Exist for Allergy Treatment in Diabetic Dogs? 
• How to Combat SeasonalAllergiesin Dogs 
• Is Your Flea Control Product Hurting Your Dog? 
• 10 Tips for Keeping Your Home Flea-Free 
• Why Are People Spending Thousands on Bogus Allergy Alert Dogs
• Ask a Vet: Can Dogs Be Allergic to Cats (and Vice Versa)? 
• Parasites 101: Flea and Tick Control
• Dog Flea and Tick Treatment Options 

Learn more about dogs with Dogster:

• 9 Tips for Keeping Your Dog Cool This Summer
• Let’s Talk: Does Your Dog Love to Roll in Stinky Things?
• Be Polite to Your Dog — It Benefits Both of You

Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)