An itch for something to eat
On Presidents Day, my kids and I baked silly cookies. We rolled out dough and cut out head shapes. Making noses and ears out of bits of dough, we finished them off with eyes, mouths, beards, and hair created with nuts, raisins, and chocolate chips. The next day when I started to pack George and Abe into their lunch boxes, I was chided. "Mooommmmmm," Sydney complained. "I'll have to sit at the Peanut Table."
Food allergies. According to the Mayo Clinic, approximately two percent of adults and six percent of children have true food allergies, and they are becoming more prevalent. Now just because you have a bad reaction to a particular item on the menu doesn't mean you are allergic. Tomatoes may give you acid indigestion. Milk may give you the runs.
These are not true allergies but rather defined as food intolerance. A true allergy involves triggering of the immune system. In people, the most common food allergies are eggs, peanuts, fish, shellfish and tree nuts. Children also are frequently allergic to cows' milk, wheat and soybeans. So what about George Washington, the Westie, or Abe Lincoln, the Abyssinian? Could they have food allergies? Is it okay to feed Abe that Yummy Shrimp Feast or to give George his pills in peanut butter?
Food allergies are fairly common in dogs and cats, but unlike the life-threatening reactions we hear about in people, prompting the designation of "peanut-free" areas at schools, and more and more people packing Epi-pens in their purses, in pets food allergies typically present as non-seasonal pruritus. (Pruritus is the technical term for the feeling of wanting to scratch.) Now before you blame the dog chow for George's scratching, there are other things to consider. The most prevalent pruritic skin disease in pets is fleabite allergic dermatitis. Just yesterday I spoke on the phone with a client whose golden doodle was scratching and scratching even though she assured me, "he doesn't have any fleas." Later that morning, she brought him in for me to check. You guessed it. Fleas. I didn't see bugs hopping about but did find the telltale little black specks in his coat. No, not dirt from the garden. Flea excrement. Want to prove it? Put a few pieces on a wet paper towel. Fleas eat blood so flea poop has red pigment in it. If that black speck is flea dirt, it will develop a rusty reddish ring around it.
Okay, you say. You use total body flea control products on your pets faithfully. You've checked carefully; there are no fleas. And they are still scratching. The next most common pruritic skin disease is called atopy and is caused by inhalant allergies. George may be allergic to pollen, mold, house dust mites, tobacco smoke (shame on you for smoking), or a host of other things. Your veterinarian can discuss the available diagnostic tests, or you may opt to treat George's symptoms without pinning down the cause, especially since some of these allergies are seasonal and clear up quickly when pollen season passes, or when we air our houses in the spring. If George has multiple or severe inhalant allergies, your veterinarian can help you strategize about avoidance, desensitization, and symptom control.
Let's get down to food allergies. Age of onset varies, but up to half of cases in dogs develop by one year of age and by two years in cats. However, symptoms can develop much later in life. Some breeds may be predisposed, including Labradors, Cocker Spaniels, Golden Retrievers, Wheaten Terriers, Dalmatians, Shar-Peis, Lhasas, Springers, Miniature Schnauzers, Dachshunds, German Shepherds, and Siamese cats. Food allergies in pets tend to come on gradually. George will scratch, lick, and chew particularly at his face, ears, legs, paws, and underbelly. His skin may be red and raw from self-trauma. Over time, the skin becomes thickened and develops dark pigmentation from the chronic irritation. Secondary bacterial and yeast infections are common. Some dogs exhibit nothing more than chronic ear infections. Cats tend to self-mutilate even more than dogs and often develop distinct lesions known as eosinophilic plaques or granulomas. These are linear or irregular red patches on the legs, sides, or underbelly, or swollen, eroded lesions on the lips.
Although it is possible to run blood tests for food allergies, this method may yield significant numbers of false positives or false negatives. I like to use these tests to get a starting point but the gold standard for diagnosis is feeding a strict elimination diet for six to twelve weeks and see if symptoms resolve. This does not mean simply going to the grocery store and picking out a different brand of chow.
A true elimination diet is composed of a novel protein and a novel carbohydrate to which the pet has never been previously exposed. In the old days, that meant lamb and rice, which were not originally staples of the pet food industry. Consumers drew the erroneous conclusion that lamb and rice were inherently less likely to provoke allergies. This is just not the case.
Your veterinarian can help you navigate through the seas of special diets available such as rabbit and green pea, or duck and potato. There is a Hills Prescription diet called Z/D in which all the proteins have been processed in such a way as to make them too small to provoke an immune reaction. One client made her own elimination menu by home cooking local venison and potato. Whichever diet you choose, it is essential to avoid all other foods completely. No treats. No rawhide chews. Not even any flavored supplements or medications. Just like people with peanut allergies, the tiniest bit of allergen can elicit a reaction.
If George's skin improves after a few months on the elimination diet, we have a presumptive diagnosis. (Sometimes we can be fooled if we happen to begin the food trial at the same time as a seasonal allergen is disappearing.) Once our trial is concluded, it's time to start adding foods back in one at a time. Again, this doesn't mean just buying a new brand. It's like introducing new foods to a toddler. Add one specific item at a time, and then wait a few weeks to make sure George doesn't get itchy again. Maybe try chicken first. Still fine? How about soy? Beef? Fish? Corn? You get the idea.
The main reason an elimination diet fails as both diagnostic tool and treatment is lack of client compliance. You just can't resist letting Abe lick your plate or giving George the end of your sandwich. Even a dog biscuit can ruin the plan. Another complicating factor is the frequency of multiple allergies. George may very well have inhalant allergies as well as food allergies. Thus his symptoms may not resolve completely on a hypoallergenic diet, and may worsen seasonally. But if your pet seems fifty per cent better on the elimination diet, that is good evidence that food allergy is at least part of the problem.
There is some controversy over whether food allergies in pets also cause gastrointestinal problems such as vomiting and diarrhea. If George develops hives or any dramatic symptoms like difficulty breathing, consult your veterinarian immediately. The good news is that, unlike in humans, food allergies in pets are rarely life-threatening. Once diagnosed, discuss long-term options with your veterinarian. Home-cooked diets are not always balanced for lifelong nutrition, but there are plenty of good commercial products available and many pets can be returned to over-the-counter brands once the offending foods have been identified. Now I think I'll go have a cup of tea and a nutty Presidential cookie. No allergies here.