What is My Pet Allergic To? Part 2 – FOOD

Yesterday, I saw one of my favorite patients – a super-sweet, chocolate Labrador Retriever. He had yet another ear infection and constant licking and scratching. Grandma and grandpa were over last weekend and they just can’t resist sneaking some of their dinner left-overs when those sad eyes stare longingly at them. Problem is… our sweet Labrador is allergic to chicken so now we have started the cycle of itching and infection all over again.

Today, we will discuss food allergies that cause chronic skin and ear problems. (Sensitivities to food that cause signs such as vomiting and diarrhea or conditions, such as inflammatory bowel disease, will be saved for a later post.)

So how do you know if your pet is allergic to a specific food?

If your pet has chronic skin and/or ear problems, your veterinarian will likely be suspicious of an underlying allergy. But what is your pet allergic to? First, as discussed in the previous post, make sure to rule out the possibility of a flea allergy. You don’t want to spend a lot of time, money, and energy chasing down a difficult to determine allergen, only to find that a flea allergy was the problem all along.

Next, your veterinarian may suggest a food trial to determine if there is an allergy to an ingredient in your pet’s food. This does not mean that there is a problem with the quality of your pet’s current food. It is just that your individual pet may have an allergy to one of the ingredients, such as chicken, beef, corn, wheat, etc.

Pets that have food allergies will usually be itchy year round. This is because they usually eat the same food all the time. If your pet’s problems appear to be seasonal, a food allergy is less likely, and your veterinarian may suggest skipping a food trial and going straight to addressing potential atopic dermatitis – to be discussed in the next post.

To conduct a food trial, your veterinarian will recommend a food that you must feed your pet exclusively for three months without any other food or treats given at any time. There are strict requirements that need to be met when conducting a food trial so it is best to consult with your veterinarian.  Usually, the selected food will be based on either a “novel protein” or “hydrolyzed protein”. A novel protein is one that your pet has not been exposed to before such as venison or rabbit. A hydrolyzed protein is so small that it is unlikely to cause an allergic reaction.

Food can be homemade, but there are also several commercially available pet foods. The important thing to remember is that it must be a novel protein or hydrolyzed protein and specifically designed for food trials. A food simply labeled for sensitive skin is not suitable for a food trial. Many appropriate foods will be by prescription and a bit more expensive, but it is best to do it right the first time and then after determining the specific problem ingredient, search for other options that might work for your pet.

The most important thing during a food trial is that your pet does not receive any other food or treats during the three months of the trial. Remember that once exposed to an allergen it can cause a reaction for up to 6 weeks. So if your dog is allergic to chicken and you feed a dog biscuit treat or rawhide with chicken flavoring, your dog will react for up to six weeks and you are back to square one. Also watch out for any flavored products such as medications (heartworm pills are commonly flavored) and toothpaste that may contain the food allergen.

If your pet has successfully completed a food trial and their allergy signs have resolved, it is assumed that they have a food allergy, but the specific allergy is still not yet identified. At this point, different food ingredients can be introduced one at a time for a week’s duration, and the animal observed for any recurrence of signs. For example, you may feed your pet chicken for 1 week. Then stop feeding chicken and just feed the food trial food for 1 week. If itching, skin, or ear problems develop, it is assumed that your pet has a chicken allergy. If not, chicken is allowed and you go on to test the next possible ingredient.

If your pet’s allergic signs never resolved with the food trial, then it is assumed that it is not a food allergy and we progress to the next step in allergy identification which we will discuss in the next post – What is My Pet Allergic To? Part 3 – Atopic Dermatitis.


Why is my pet itchy?

Itching, also known as pruritus, is one of the most common presenting complaints I get from pet owners. They are frustrated listening to the incessant scratching and licking which may keep both them and their pet awake at night, and concerned that their dog or cat is uncomfortable.

Itching is a non-specific sign, meaning that there can be many different causes. However, most cases of itching can be attributed to two broad categories: infections and/or allergies. Often times, both infection and allergies may be contributing to the problem. A pet with allergies is more susceptible to secondary infections. Both are itchy and create a cycle of itching, licking, and infection.

The first step to relieving itchiness in your pet is to identify the cause. Your veterinarian will usually start by asking some relevant questions about your dog or cat, other pets and people in your household. Questions will include detailed information about the type and duration of signs and past and current medications.

Your veterinarian will perform a physical examination of your pet to determine if there are any signs of infection, such as hairloss, redness, pustules, crusts, etc. Infections can be bacterial, fungal (yeast and ringworm), or parasitic (demodex and sarcoptic mange). Diagnostic tests, such as skin cytology, fungal culture, or skin scrape, may be performed. If infection is present, it must be treated in order to determine if it is the primary cause of itching or if it is secondary to allergies or another cause.

Allergies are extremely common and are likely the cause of most cases of itchy dogs. My next posts will discuss allergies and how to treat them.