Cancer. Pet guardians fear this diagnosis above all others; not only because the conventional treatments are so perilous, but also because, despite treatment, it is most often fatal. More than half of dogs over the age of 10 will die of cancer, and the incidence of cancer in cats and younger animals is growing rapidly. As responsible guardians, we need to understand the risk factors that contribute to the development of cancer; do all we can to prevent it; and take effective action when a diagnosis of cancer is made.

Causes of Cancer in Pets

Our modern world has many conveniences, but also many hazards that simply didn’t exist a few generations ago. For example, many carcinogens (cancer-causing compounds) are now ubiquitous in air and water.

Cancer develops due to a variety of factors, many of which we cannot control. No one knows exactly what causes most cancers, but it is most likely a combination of one or more of the following factors, along with a genetic predisposition or sensitivity that makes a particular dog or cat susceptible to cancer (more detailed discussions can be found below the list):

General Factors

  • Age (older animals are more prone to develop cancer)
  • Breed (e.g., Boxers and Golden Retrievers are prone to develop lymphoma; giant breed dogs are more apt to develop bone cancer)
  • Genetic mutations
  • Over-vaccination (especially with killed vaccines, which contain toxic adjuvants such as mercury and aluminum)
  • Pharmaceuticals
  • Retroviruses (in cats)
  • Chronic inflammation
  • Oxidative cellular damage
  • Obesity
  • Stress

Environmental Toxins

  • Cleaning products
  • EMFs  (electromagnetic fields) and other sources of radiation, including sunlight
  • Chemical emissions (e.g., flame retardants and plastics from computers, flooring, clothing, furniture, carpets)
  • Air pollution – outdoor and indoor
  • Pesticides and other chemicals
  • Air fresheners
  • Second-hand smoke (especially in cats and long-nosed dogs, such as collies and greyhounds)

How serious are environmental toxins? A recent report by the Environmental Working Group found 48 chemicals in pets’ blood (out of 70 tested for); 43 of them reached levels far higher than in people: 5 times as much mercury; 2-1/2 times more perfluoro­chemicals in dogs (from stain- and grease-proof coatings), and 23 times more fire retardants in cats.

Food toxins

Many pets ingest a host of toxins through their everyday diet. Here are just a few of the potential toxins in commercial pet food:

  • Acrylamides, trans fats, and other carcinogenic factors used or created during the manufacturing of dry kibble.
  • Chemicals in food and treat packaging, such as BPA and other plastics.
  • Bacteria are present on virtually all dry pet foods; some, like Salmonella, produce their own toxins and can make pets very ill.
  • Contamination with chemical fumigants applied during storage and transportation.
  • Genetically modified (GMO) ingredients (94% of soy; 70% of corn; 74% of cottonseed oil; 80% of canola oil in the U.S. are GMO). GMOs damage the primary detoxification organs (liver and kidneys).
  • Persistent Organic Pollutants (POPs) are persistent and ubiquitous around the world; they are linked to several human cancers. POPs are found in fish, animal fats, and other animal products used in pet food.
  • Antibiotics and other drugs are used in livestock, and may persist throughout pet food processing.
  • Crops condemned for human consumption due to excessive pesticide or fertilizer residue may be used without limit in pet food.
  • Molds and mold toxins are common contaminants of corn and other grains. At least one of these, Aflatoxin B1, is known to cause liver cancer.
  • 27 categories of “food enhancers” are allowed in pet food, including preservatives, texturizers, colorants, emulsifiers, binders, stabilizers, thickeners, surfactants, and lubricants.

Signs of Cancer

How can you tell if your pet has cancer? Many cancers are difficult to detect early. Most cancers will not show up on blood tests. But there are some signs to look for, especially in older pets.

1. New or changing lumps or bumps. Most skin tumors in dogs are benign, while in cats the opposite is true. But even your veterinarian can’t tell just by looking or feeling.  Your dog may have a dozen lipomas (benign fatty tumors), but the next one could be different. Any new lump, or one that is noticeably changing or growing, should be either aspirated or biopsied to make sure it’s not cancer.

2. Weight loss not related to diet. Obesity is a huge problem in pets, and if your pet is losing weight because you are feeding or exercising her differently, that’s a good thing! But weight loss for no apparent reason is a hallmark of cancer, although it can also signify conditions like diabetes or kidney disease. Regardless of the cause, a visit to the veterinarian is in order.

3. Changes in activity level, behavior, or temperament; e.g., getting grumpier in general, becoming reluctant to move, not wanting to be handled or held, or withdrawing from normal activities or social interactions.

4. Changes is urination or defection. If you notice blood or mucus in the stool or urine; or if your pet is straining or develops diarrhea or constipation, your veterinarian needs to investigate whether cancer could be the cause.

5. Non-healing wounds. Sores, wounds, or rashes that never seem to heal can be a sign of skin cancer. A scrape, aspiration, or biopsy should be performed.

6. New or excessive drooling. Dental disease is a common cause of excessive salivation, but it can also be caused by tumors in the mouth, which are more common than you think. A tumor in the back of the mouth or throat can also cause difficulty in swallowing.

7. Bloating (abdominal distention). If your pet gradually seems to be getting bigger around the middle (as distinguished from sudden bloating caused by twisting of the stomach in deep-chested dogs), the reason could be a growing tumor. Radiographs (x-rays) or abdominal ultrasound can help find the cause.

8. Changes in breathing. Rough-sounding or faster breathing may indicate tumor(s) in the chest. Many kinds of tumors will metastasize to the lungs, so this is something that needs to be checked out immediately. In cats, a respiratory rate (breaths per minute) over 30 needs veterinary attention.

9. Spots or “freckles” in the eyes. Many animals develop black spots or freckles on the iris (colored part) of the eye, especially orange cats. These can be little melanomas, an aggressive cancer that we usually associate with skin. If any spots are new, growing or changing in character, your veterinarian needs to check them out. 

Prevention and Treatment: Two Sides of the Same Coin

Conventional cancer treatments like radiation, surgery, and chemotherapy may destroy the cancer, but there’s a trade-off in side effects; the risk-benefit ratio must be considered. And even the most cutting-edge therapies may only prolong a pet’s life without curing the cancer. Quality of life issues also impact the choice of treatments, once cancer has invaded.

Recent research suggests that the basis of many cancers is a chronic inflammatory process. And indeed, many of the factors involved in the development of cancer do cause chronic, low-grade inflammation. Such inflammation not only kills cells directly, but also deposits toxic inflammatory by-products and other “sludge” in the extracellular matrix that surrounds the cells. This toxic build-up hinders the flow of oxygen, nutrients, and wastes between cells and the bloodstream, thus creating a fertile environment for abnormal cells that can thrive in such damaged environments.

Preventing and resolving inflammation and clearing the matrix are primary goals of holistic programs to prevent or treat cancer. In fact, holistic prevention and treatment of cancer involve many of the same components:

Providing an optimal diet based on fresh, whole foods. Most commercial pet foods (especially dry foods) are made with the leftovers and unwanted parts from livestock slaughter and processing, and loaded with additives and preservatives. Due to their sensitive urinary system, cats should not be fed any dry food at all; canned is acceptable, but homemade is best.

Offering only clean, purified water. Plenty of clean water is essential to the body’s ability to resolve inflammation, and to clean up dead cells, inflammatory markers, and other waste products. (See

Limiting vaccinations. The antibodies produced by vaccines cause inflammation throughout the body, particularly in connective tissue; and every additional booster perpetuates it.

Reducing indoor air pollution, home and yard chemicals, and other sources of toxic exposure. This will calm the over-reactivity of the immune system and allow the body to cleanse and heal. See our article on green cleaning.

Minimizing electromagnetic radiation. Limit this cause of low-grade, chronic inflammation in and around your home.

Using a safe, non-toxic flea control program. Most flea products are pesticides that can contribute to the toxic overload of the body and inhibit natural cleansing processes. See our article on keeping your pet pest-free.

Minimizing stress. It’s been abundantly proven that stress suppresses the immune system. Two great ways to do this are exercise and flower essences.

Providing adequate exercise. Regular physical activity is a natural immune booster and stress reducer. Interactive play is a wonderful way to enhance your bond with your cat and have fun at the same time.

While we may not be able to do much about air pollution or background radiation, let’s look at the factors we can control in more detail.

Diet & Nutrition

Any cancer prevention or treatment program begins with diet. All the treatments in the world will not help a patient who eats “junk food” (as many commercial pet foods are!). The foundation of health is a balanced, home-prepared diet of fresh, organic, whole foods. When the body is supported with the building blocks needed to maintain healthy cells and repair damaged ones, healing from within can begin.

Many types of cancer cells—particularly lymphoma—utilize glucose from carbohydrates as fuel. Limit the fuel, and the cancer’s growth will also be limited. A low-carbohydrate diet can be very helpful in fighting cancer. Additionally, many cancer cells cannot utilize fat as an energy source; so more and better quality fats in the diet will help combat the cachexia (weight loss and muscle wasting) that commonly occurs in cancer patients. Holistic veterinarians frequently recommend a diet that is low-carbohydrate, moderate protein, and moderate to high fat for cancer patients.

The most harmful carbohydrates come from processed grains, fructose-containing fruits, and starchy vegetables such as white potatoes and peas. Dry kibble must contain starch due to processing requirements; so in general, dry food should be avoided. Veggies with higher levels of fiber and plenty of antioxidants are better choices.

For dogs, a diet of roughly 50% meat, and 40–50% non-starchy vegetables is optimal.For cats, a diet of 80% meat (cats can tolerate fattier meats than dogs) and 20% non-starchy vegetables is recommended, again with fish oil added for additional fat. For both dogs and cats, supplementation with vitamins, minerals, marine-source Omega-3 essential fatty acids, and antioxidants should also be part of the daily diet.

A high-quality Omega-3 oil (green-lipped mussel, cod liver or fish oil) will provide additional fat, which helps prevent cancer cachexia (wasting); the bonus is Omega-3s’powerful antioxidant and anti-inflammatory properties.

When a home-prepared diet is not possible, try ready-made (frozen) raw food, freeze-dried or dehydrated diets, or a very high quality low-carbohydrate canned food. Meat can be lightly cooked without losing nutrients.

If processed foods are used, consider adding fresh, ground or minced meats, and (for dogs) pureed or steamed non-starchy vegetables and/or high antioxidant value, low fructose fruits. Dark leafy greens (kale, chard, collard greens), broccoli, carrots, and berries contain antioxidants that are beneficial in fighting cancer. Another good source of green nutrition, as well as antioxidants, is blue-green algae such as BioSuperfood or BioPreparation.

One other significant dietary issue needs mentioning, and that is weight management. Overweight pets are at increased risk of many diseases, such as arthritis, diabetes, and heart disease as well as cancer. Food does not equal love; your pet would rather have quality time with you than a big dinner or a few extra treats. Body fat doesn’t just sit there quietly; it continually churns out inflammatory signals that can contribute to tumor formation. Keeping your pet at an ideal weight is an essential part of a healthy lifestyle.


Depending on where you live, the quality of tap or well water ranges from wholesome to highly toxic. Distilled water is not suitable for long-term consumption because it pulls minerals from the body; but it can be used in a short-term detoxification program that is closely monitored by your veterinarian.

Reverse-osmosis filtered water is top choice, followed by natural spring water. However, bottled water can leach toxic chemicals from the plastic into the water; be sure it is BPA free. The animal’s water needs to be kept clean and fresh at all times. If your pet is not a great water drinker, add extra water to the food, or try a non-plastic pet fountain. Wet foods, including homemade, reconstituted freeze-dried, and raw diets, are also important sources of moisture.
Many cats who eat only wet food will not drink water very often because, like their wild cousins, they get most of their water from their food.


Many holistic veterinarians agree that over-vaccination is a significant contributor to the rising rates of chronic disease and cancer in cats and dogs. This is not to say that pets should not receive any vaccines—puppy and kitten vaccines against life-threatening diseases are still important; and rabies vaccination is required by law. But most pets in the U.S. receive many unnecessary vaccines over their lifetimes. Some cancers, such as vaccine-associated sarcomas in cats (and occasionally in dogs and ferrets), are directly caused by killed vaccines (which include rabies, feline leukemia, and FIV). Most booster vaccines (other than legally mandated rabies vaccines) are unnecessary for adult pets. If your veterinarian recommends multiple or annual vaccinations, consider finding one who is more aware of the risks.

Moreover, every vaccine is labeled “For use in healthy animals only.” Any animal diagnosed with cancer (or any chronic disease) or exhibiting signs of a weakened immune system should not be vaccinated at all. For more information please read our in-depth article on Vaccination.

Home Pollution

Indoor air pollution has gotten a lot of press lately; it can be even worse than outdoor air pollution from cars, factories, and agriculture. For our companions’ sake, it is important to examine our home and yard care practices. Cleaning products are the first place to look; if the floor or carpet cleaner you use contains toxic chemicals (as most do), and your companion’s nose is continually close to that floor (as most are), then the body must continually detoxify itself. Choosing homemade, natural, and green cleaning products can go a long way to limiting the toxins your companion accumulates.

Spray and plug-in air fresheners and scented candles are popular with some pet owners to help cover up that “pet” smell, but they constantly release toxins (such as formaldehyde, camphor, ethanol, phenol, and petrochemicals) into the air our companions breathe. They are unnecessary and should not be used. There are many natural alternatives, including essential oil diffusers and spritzers, HEPA air filters, organic herbal sachets and potpourris, and fresh aromatic plants. However, keep in mind that pets are far more sensitive to smells than we humans. Cats in particular may be repelled by citrus, pine, and other scents; always provide a place where pets can escape odors they don’t like.

Yards and other green spaces are another area of toxic exposure to our companions. Chemical fertilizers, pesticides, herbicides, and similar products around the home should be eliminated. There are abundant non-toxic alternatives available today.

Electromagnetic Radiation

Ongoing research suggests a link between electromagnetic radiation and cellular changes that can lead to cancer. Sources of electromagnetic radiation include sunlight, cell phone and broadcasting towers, underground and aboveground power cables (ambient sources outside our control); but also home wiring, electrical cords and outlets, microwave ovens, appliances, cordless and cellular phones, computer monitors, and televisions. This is especially relevant for cats, who love to curl up in warm places like the top of the cable box or computer monitor.

Keep your companion’s bed as far away from electrical components as possible. At night, make sure all electronics are turned off. This is important not just for the radiation, but also light. Even the tiny glow from power indicators can be disruptive to sleep, and inhibit the body’s natural healing cycles.

Pest Control

Flea and tick management is an essential part of health, but spot-on flea control products such as Advantage, Frontline, and Revolution, are heavy-duty pesticides. These poisons absorb through the skin permeate the animal’s system; while a portion of them is eliminated in through urine and feces, some components may not be fully cleared, and can contribute to the toxic sludge build-up in the extracellular matrix. Tablets given by mouth are no better. A recent report from the U.S. Environmental Protection Agency makes it clear that every commercial flea product can cause illness and even death in pets; the agency is now encouraging more truthful labeling, but it is not requiring safer products.

There are many natural flea/tick control products that offer effective, non-toxic alternatives to chemical pesticides. They take slightly more effort than putting occasionally a few drops on your companion’s skin, but they are well worth it for the long-term health of your friend.


You may look at the cat sprawled in a patch of sunlight, or the dog curled up at your feet, and wonder, “How can this animal be stressed?” Yet our furry companions can and do experience stress, as much or more than we do. For instance, dogs with separation anxiety live in extreme stress every day their guardians go to work or school. Cats in multiple-cat households are frequently stressed over territorial competition.

Of course, both cats and dogs are acutely aware of the stress levels of their human companions—the more stressed you and other family members are, the more your cat or dog feels, absorbs, and manifests that stress—whether by acting out behaviorally or internalizing it as illness or cancer. Managing our own stress may be the most important step we can take to improve our pets’ well-being.

For dogs, one of the best ways to reduce their stress is proper training. Every puppy should go through a “puppy class” for basic obedience and socialization. Even if you adopt an older dog, both you and the dog can benefit from a consultation with a good trainer or behaviorist. These professionals help you interpret the dog’s behavior and teach you how to communicate in ways that your dog can understand. A well-trained dog is a secure dog—and a much safer one as well.

Cats are not as easily trained (although it’s not impossible, and can be very beneficial for young cats, as well as active breeds, like Orientals and Bengals). But you can reduce cats’ stress in other holistic ways, such as energy therapies, Tellington TTouch, massage, and flower essences.

“Indoor enrichment” can be helpful for both dogs and cats to reduce mental and emotional stress. This may include: food-dispensing toys; sensory enrichment (such as a window perch for bird-watching, pet-directed videos, and cat furniture for climbing and scratching, as well as to increase vertical territory); and novel objects (like cardboard boxes or paper bags). But adequate quality play and petting time with the human family is truly the most important “enrichment” tool.


You need it, and your pet needs it. Exercise is one of the best ways to combat stress, and is also crucial for the health of the mind and body—human, dog, or cat. In their natural state, canids and felids roam large territories and hunt for a living. The more we can mimic this natural lifestyle, the better.

Play is wonderful, because s it provides both exercise and the joy of fun and laughter (on your part!). There is nothing more hilarious than the antics of a cat chasing a laser beam or feathers on a pole or string. Cats need exercise as much as dogs do, and regular play sessions are the ideal way to accomplish it. Or, try a kitty harness and go for walks. Introduce this activity gradually to increase the chance of acceptance.

Dogs are fairly easy to exercise; a simple walk will do you both good! A play date with another dog or a romp at the dog park can be great exercise as well as mental stimulation and stress relief. If your dog is a firm believer in staying home, then play fetch in the house, or find some other way to provide exercise every day. But don’t overdo it…if your dog has been playing couch potato, start slowly and gradually increase exercise intensity as much as can be tolerated.

Physical activity is vital for pets for weight control, digestive health, detoxification, immune health, muscle tone, respiratory health, and mental and emotional stability.

Holistic Treatment of Cancer

A diagnosis of cancer in your beloved companion requires many difficult choices. You will surely forget to ask many important questions when you first hear the dreaded word, so schedule a follow-up visit with your veterinarian to discuss the issues that are likely to arise. Try not to make any profound decisions until you have a chance to educate yourself about all the options available—both conventional and alternative. Ask for a referral to an oncologist who can answer questions about conventional treatment methods. Find a holistic veterinarian, either in your area or one who will provide phone consultations, regarding alternative cancer treatments. Cancer is serious business, and an integrative team approach is best.

For many cancer patients, conventional treatment options are as harmful than the cancer itself. In these cases, holistic treatment can offer the chance for a better quality of life, even if it cannot cure the cancer. Holistic care aims to provide the animal with the resources its body needs to heal from within.

Every case is different. There is no one way to treat any type of cancer, although the above suggestions can help no matter what type of cancer the animal has. There are also some basic immune-boosting, anti-inflammatory, cancer-fighting nutritional supplements that can help in many cases.

Diet, of course, is fundamental. You can give supplements all day long, but if the basic diet is “junk food,” you’re just throwing good money after bad, and needlessly stressing your pet.

Helpful supplements include:

Digestive enzymes – they help fight inflammation, as well as help the digestive system break down and more easily absorb the urgently needed nutrients in the food.

Omega-3 Fatty Acids(from marine sources) these are some of nature’s most potent anti-inflammatories. These fats are crucial for immune and nervous system function, and are necessary for rebuilding cell membranes. Nordic Naturals makes the best quality fish and cod liver oils for pets; and for fussy pets, Moxxor produces green-lipped mussel oil in tiny capsules suitable for cats and small dogs.

Antioxidants – prevent oxidative damage (which promotes ongoing inflammation) and increase immune function. They help prevent cell and tissue injury by scavenging and destroying free radicals, and play a fundamental role in cancer prevention and control. Vitamins A, C, and E are the best-known antioxidants. Other powerful antioxidants include green tea extract, co-enzyme Q10 (which reduces free radical production at the source), N-acetylcysteine, proanthocyanidins, flavonoids, carotenoids, and quercetin [but avoid alpha-lipoic acid for cats, as it can quickly build up to toxic levels]. Only Natural Pet makes an excellent antioxidant blend for dogs and cats that also contains herbs and medicinal mushrooms (see below). Curcumin, from the Indian spice turmeric, warrants special mention, as it also inhibits tumor growth and metastasis, and can reduce the side effects of chemotherapy.

Caution: some oncologists recommend against antioxidants for pets during conventional therapies such as radiation or certain types of chemotherapy, so check with your veterinarian before supplementing with antioxidants.

Medicinal mushrooms – are an important part of Traditional Chinese Medicine, and contain powerful immune-modulating compounds such as beta-glucans. Many holistic practitioners incorporate them into their anti-cancer protocols.

Herbs – many herbs are renowned for their cleansing, tonic, anti-tumor, or anti-cancer effects. However, herbs can be extremely powerful and may carry the risk of serious toxicity, so always work with a trained veterinarian to ensure safe use.

There are two “standard” herbal formulas widely used in cancer care: Essiac and the Hoxsey Formula. Both are named for the original formulators of the herbal compounds (although Essiac is the formulator’s last name, Caisse, spelled backwards). Ojibwa Tea of Life makes organic herbal formulas for pets.

Homeopathy – Constitutional homeopathy is often very helpful in treating cancer. Several homeopaths have had great success in treating some cancers with homeopathy alone. It has a good safety record, and is very easy to administer. Treatment is very specific to each individual and must be guided by a veterinarian trained in homeopathy.

Homotoxicology –Homotoxicology is an offshoot of homeopathy that focuses specifically on detoxification, organ support, and alleviation of symptoms.

Acupuncture/Traditional Chinese Medicine – Acupuncture is very helpful for pain relief in cancer patients. It can stimulate the immune system and assist in promoting detoxification as well. Chinese herbs are also used for cancer therapy.

For a list of holistic veterinarians in your area, see the American Holistic Veterinary Medical Association referral directory, the Academy of Veterinary Homeopathy, or the International Veterinary Acupuncture Society.


While cancer is a frightening diagnosis, there is much that can be done to improve the quality of your companion’s life and potentially extend the amount of time you have with him or her. Keep in mind that it is crucial to remain as optimistic as possible. A positive attitude is not just wishful thinking; it is completely practical. Use E.F.T. or flower essences to help both you and your pet maintain emotional balance. Remember, your companion senses your stress. All therapies will go farther when administered with large doses of love and affection.