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Myth About Illness


This article is not intended to provide veterinary medical advice, but rather to examine common potential indications of health circumstances in pets caused by issues other than commercial pet food. In the event of a veterinary medical emergency or suspected emergency, pet owners should seek professional advice immediately. In all the types of situations listed below, a veterinarian should be consulted if a symptom persists.

Healthy, happy pets

Cats and dogs are faithful, loving companions that bring countless benefits to pet owners. Most dogs and cats live long, healthy lives free of serious health issues. Although they cannot speak, at least in human languages, they can tell us when they are not feeling quite right through the symptoms they exhibit. A veterinarian can diagnose a potential health issue in pets and develop a treatment plan.

In the event a veterinarian believes an issue may be related to food, pet owners can assist in the process of narrowing down a potential cause by helping a veterinarian develop a complete diet history. A complete diet history should include all of the items a pet has or may have consumed, whether it is a commercial pet food product, a human food, something yucky on its walk, or something from the neighbor’s trash bag.

When a person gets sick, they ask themselves questions like:
Did I get too close to Johnnie when he had the sniffles?
Was it from all the time I spent on a plane during my business trip?
Did I catch it from that person who was sneezing on the subway?
When a pet gets sick, all too often these days the statement that first gets blurted is, "It must have been the food!”

As with people, there are many different potential causes of illness in pets. Sometimes a single symptom or physical reaction can be a sign of several possible health issues. Likewise, a single health issue can manifest in different ways.

Many possible health circumstances can result from items pets have ingested that are not commercial pet food, including something picked up outdoors.

Problematic people food

Commercial pet food products are carefully formulated so they are appropriate for the species to which they are intended to be fed (i.e., cat or dog). Most commercial pet foods are nutritionally complete and balanced so they fulfill a pet’s total nutritional needs.

Aside from not being nutritionally complete and balanced, many of the foods people eat can cause serious health issues in cats and dogs. It is commonly known that chocolate and onions are toxic to dogs, but fewer pet owners realize they are toxic to cats as well. Chocolate can be fatal if eaten in sufficient quantity, and when it comes to chocolate, the purer the form, the stronger the toxicity (i.e., unsweetened dark/bakers chocolate is more toxic than milk chocolate). Pets suffering from chocolate poisoning may exhibit vomiting, diarrhea, increased urination, hyperactivity, heart arrhythmia, tremors and seizures.

Onions, along with leeks and other alliums, cause hemolytic anemia, or breakdown of the body’s red blood cells, and it only takes a small amount to poison a pet. Symptoms of hemolytic anemia can include breathlessness, lethargy, diarrhea and vomiting.

Other human foods can also be harmful to pets. On the list are grapes and raisins, nutmeg, macadamia nuts, caffeinated products, alcohol, yeast/unbaked dough, and xylitol-sweetened products.

A final note on the matter of ingested toxic substances, in the event a pet owner is instructed by a veterinarian or poison control worker to induce vomiting by administering hydrogen peroxide, such a treatment is best done outdoors, as the pet will have an immediate reaction.

Human foods not mentioned above can also be detrimental to pets. Many of the foods people eat contain too much fat, salt and spices to be appropriate for pets. Feeding such items can cause gastrointestinal problems and other health issues. Fed over a long period of time, human foods can be a significant contributing factor to pets becoming overweight and obese.

Loose stool/diarrhea

Cats and dogs have sensitive digestive systems that can be thrown off balance from changes in diet. For this reason, it is recommended that changes in the type of food given to a pet occur gradually over a number of days. By this method, an increasing amount of the new food is fed at the same time that the old food is fed in a decreasing amount.

Similarly, giving human food to a pet can cause a pet to suffer from diarrhea. This may be because the food throws off the pet’s gastrointestinal routine, similar to an instance of a sudden dietary transition, or because of the properties of the food (e.g., too fatty or too spicy). Dairy products can also cause diarrhea in pets, as many adult cats and dogs are unable to digest lactose, the natural sugar found within dairy products. On this point, cheese flavorings used in pet food products are not an issue.

Diarrhea can also be a sign of more serious health conditions, including bacterial or viral infection, cancer, kidney or liver disease, and parasites. If a pet’s diarrhea is black, it could be a sign of internal bleeding in the digestive tract.


Dogs can vomit for many reasons. Vomiting can be a sign of a serious health problem — such as a swallowed foreign object, parasites and tumors — particularly if it does not stop or if a pet vomits up a yellowish fluid, which is bile, rather than food.

Vomiting can result from the way a pet eats or drinks, rather than what they consume. If a dog or cat eats or drinks water too quickly, or if they consume too much at one time, pet owners may find themselves cleaning up a mess.

Cats can be susceptible to the formation of hairballs, as any cat owner who has found a hairball on the floor can attest. Pet food companies make food products and treats designed to control the formation of hairballs.

Dogs and cats that eat grass or other plants often regurgitate the plant matter as a messy pile. Pet owners should be mindful that many indoor plants — such as peace lily, aloe vera, and asparagus fern — can be toxic to pets. Products are available on the market to help deter pets from chewing on plants, as well as other household items such as furniture, electrical cords and shoes.

Hair loss (alopecia)

Dogs can lose hair for numerous reasons, including mange, bacterial or fungal infections, excessive grooming and hormonal imbalance (e.g., hypothyroidism and estrogen imbalance). Cats too are susceptible to hair loss; in addition to those causes listed for dogs, older cats that have been diagnosed with cancer may also experience alopecia.

Itching (pruritis)

Itching can be the sign of several possible health conditions. Some pets have environmental hypersensitivities, including reactions to grasses. Fleas, ticks, and mites (which can cause mange, scabies and "walking dandruff”) are parasites that can afflict cats and dogs. In the case of fleas, itchiness can persist long after the offending bite is delivered in animals allergic to flea saliva. Bacterial and fungal infections are also common causes of pruritis in cats and dogs.

Out page on the "Allergy Myth” explores misconceptions about allergies in pets, and in-cludes additional information on pruritis.


Lethargy is a generic symptom associated with a long list of health conditions such as bacterial or viral infections (kennel cough, parvovirus, distemper, influenza, Tyzzer disease, etc.), heartworm, hypothyroidism, Cushing’s disease, heart disease, liver disease, kidney disease, diabetes, hypoglycemia, anemia, tumors, and poisoning (including from onions, leeks and garlic). As with other conditions listed in this article, it is advisable to consult a veterinarian if lethargy is persistent.

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