So You Think Your Dog Has Allergies, Part 1: Symptoms and Types

When Maisy was just a wee thing, she began chewing on her legs. A quick internet search suggested that it might be food allergies, so I switched her food. And again. And again. What started as just a bit of itchiness evolved into almost a year of frustration.

As it turns out, the subject of canine allergies is complex, and internet advice is often simplistic and lacking vital information. That’s why I decided to tackle a three-part series on the topic. Of course, I am not a vet, so this is not medical advice. Instead, it is a sharing of information from one owner of a dog with allergies to another. If you think your dog might have allergies, I highly recommend you schedule an appointment with your vet because there are a number of other skin problems that can look like allergies but are not.

Signs Your Dog Has Allergies
So, what do allergies look like in dogs? Well, unlike in humans, dogs typically don’t have nasal congestion. Runny noses, sneezing, wheezing, or eye discharge may be a symptom of allergies, but it probably isn’t. See your vet. Instead, dogs with allergies are itchy. What you will see is excessive scratching, licking, and chewing. This typically happens on the feet, face, and groin, but may show up anywhere.

Unfortunately, these behaviors can result in secondary problems, most often skin infections or ear infections. Before we got a handle on Maisy’s allergies, she chewed off most of the fur on her front legs, and had some scabs. It was pretty ugly, actually, and we did need to treat her with antibiotics to help clear it up.

Her left leg is bare and the skin is being damaged because she was chewing it so much.

Allergy Cause #1: Flea Bites
The most common of these causes is flea bites. According to research cited in the April 2011 Whole Dog Journal article Itching to be Well by Nancy Kerns, approximately 40% of dogs have an allergy to fleas. Of course, if a dog is bit by a flea, it’s going to itch either way. However, a dog who is truly allergic will have an overreaction. If you have found only a few fleas, but your dog has widespread redness- or worse, oozing sores- it’s likely he’s allergic. The bad news is that dogs who suffer from a flea allergy tend to get worse throughout their lives.

Allergy Cause #2: Environmental
Environmental allergies happen when a dog has an itchy reaction to something he has either inhaled or been transcutaneously exposed to. Things like mold, dust, and pollen are common, although poor Maisy is also allergic to- are you ready?- human dander. (Yes, that's possible. Yes, I cried when I found out.)

According to the Whole Dog Journal article, approximately 10% to 15% of dogs have an environmental allergy. 80% of these dogs will also have a flea bite allergy (for once, Maisy has beaten the odds!). If your dog has an environmental allergy, it’s highly likely you’ll know it while he’s still young- 75% of dogs will show symptoms before three years of age, although the first year tends to be fairly mild.

Allergy Cause #3: Food
Food allergies are actually quite rare, although the exact prevalence is contested. A conservative estimate is that 1% to 5% of dogs have food allergies, possibly up to 10%, but the Whole Dog Journal reviewed research that suggests up to 43% of dogs are sensitive to some food item. 43% of these dogs will also have another type of allergy.

Food allergies are unique in that they typically affect more than just the skin. 10 to 15% of dogs will also have gastrointestinal symptoms like diarrhea, vomiting, excessive gas, and cramping, and a dog with food allergies might also be affected in the respiratory tract or central nervous system. This means that diagnosis can be tricky; you definitely want to visit your vet.

Although food allergies can begin at any time in life, generalized itchiness that begins before six months of age is very probably caused by food. This is absolutely true for Maisy- she was right around five or six months when we first noticed the excessive itching. Of course, this was complicated by the fact that her birthday was in the fall, meaning that Maisy hit her six month birthday at the height of allergy season- the spring.


So, how did I determine what her allergies were? Well, it was an incredibly frustrating process. I learned a lot during it, though, and in my next post, I’ll share some information that will helpfully make the process easier for you. Part three will discuss some of the treatment options available.

Until then, I’d love to hear from my readers. Do your dogs have allergies? Do you know what they’re allergic to? What symptoms did they have?