Building a Healthy Immune System for Dogs & Cats

Written by: Dr. Jean Hofve, Holistic Veterinarian, DVM

Natural Immune Support for Dogs & Cats

The immune system is a complex network of highly specialized tissues, organs, cells, chemical messengers, and hormones. The lymph system and lymph nodes, spleen, bone marrow, and thymus gland all play a role, as do white blood cells, antibodies, and complement proteins.

There are two main types of immunity, innate and acquired. Innate immunity is the body’s built-in defense system, and includes the skin, immune cells and organs, the linings of the gastrointestinal, urinary, and respiratory tracts, mucous secretions, and stomach acid. Innate immunity is a non-specific barrier against injury and infection.

Acquired or adaptive immunity involves the immune system’s further defenses against specific invaders that are created as the body encounters different pathogens through exposure, illness, or vaccination. The immune system develops a memory of each disease it fights and is able to quickly recognize and defend against the pathogen the next time it appears.

Symptoms of a weakened immune system include skin infections, recurring parasitic infections, and initially mild infections or illnesses that progress into serious health issues because the body cannot sufficiently defend itself. For cats, frequent eye or upper respiratory infections are also indicative of a weak immune system.

Proper Diet Builds the Immune System

Diet is always the first line of defense. As you have probably read before in our other articles, diet is the foundation of health. If your companion is consuming highly processed food that provides only minimal nutrition and includes toxins such as chemical preservatives, food dyes, texturizers, and other additives, his immune system is being depleted daily just to cope with that diet. Fresh, wholesome food is the first step in building a strong immune system.

Many people wait until their animal has a serious or chronic illness such as cancer, kidney disease, or allergies to finally change the diet. Prevention is so much kinder and immeasurably more effective. Please see our articleWhat You Need to Know About Your Pet’s Food for more information about proper diet. Feeding a varied diet that includes as much fresh food as possible tales more effort than scooping kibble out of a bag, but it is truly worth the effort in the long run. And an initial investment in good-quality food will end up saving a bundle in vet bills for preventable, nutrition-related diseases down the road.

One of the benefits of a healthy diet is a healthy gastrointestinal tract. If the digestive tract is stressed by inflammation from allergies or inflammatory bowel disease or other digestive disorders, the nutrients in even a healthy diet are harder to process and absorb. Healing and maintaining the digestive tract is vital to overall health and immunity. Digestive enzymes,probiotics, and essential fatty acids all play a role in gastrointestinal health and proper digestion.

Stress and Exercise

Stress suppresses the immune system. Our pets can experience emotional stress from any number of sources, such as territorial disputes among pets (especially cats), social stress, and noise and light pollution. Exercise helps reduce stress and helps build and maintain a strong body and immune system. Moderate exercise has been shown to improve immune function in humans and animals.Weight control is also key – overweight animals are much more susceptible to chronic and acute diseases and infections. Proper diet AND exercise are needed to help with weight control.

Nutritional Supplements

A good quality daily multi-vitamin and mineral supplement is a simple way to help bolster the immune system. We like to alternate the vitamin supplements we use for my cats and dogs to provide a more varied source of extra nutrition. For instance, we often give a regular multi-vitamin at one meal and a “greens” supplement at another meal. Please see our articleDaily Supplements for Healthy Companions for more information.


Antioxidants help prevent oxidative damage to cells, boost immune function, and possibly decrease the risk of infections, degenerative diseases, and cancer. Antioxidants exist as vitamins, minerals, and other compounds in foods. They act as scavengers, helping to prevent cell and tissue damage by destroying free radicals. Free radicals are highly reactive molecules that the body normally produces to defend against bacteria and other pathogens; but if left unchecked, they can damage the body at the cellular level.

Vitamins A, C, and E are the most commonly known antioxidants. Vitamin A is found in the liver and other animal tissues. It is abundant in fish liver oils such as cod liver oil. Carotene is a precursor to vitamin A found in plant material. Dogs can convert carotene to vitamin A by way of an enzyme found in the wall of the intestine. Cats, however, do not convert carotene well and must receive adequate vitamin A from animal sources. Vitamin A helps regulate the immune system by making white blood cells that destroy harmful bacteria and viruses. Vitamin A also helps maintain the integrity of skin and mucous membranes, which function as a barrier to bacteria and viruses, as well as protect against shedding of cells into the urinary tract, which can lead to the formation of stones and other urinary tract problems.

Vitamin C is the most abundant water-soluble antioxidant in the body and is manufactured in the liver and kidneys of dogs and cats. It is available from fresh or lightly cooked fruits and vegetables. Vitamin C is especially good at combating free radical formation caused by environmental toxins and other pollution.

Vitamin E is the most abundant fat-soluble antioxidant in the body. It is present in many foods including vegetable oils, cereal grains, greens, liver, and eggs. It is particularly helpful in protecting against oxidation, especially in fatty tissues.

Other powerful antioxidants include green tea, co-enzyme Q10, bioflavonoids, N-acetylcysteine, proanthocyanidins, quercitin, and curcumin (from turmeric).

Herbs, Mushrooms and Nutraceuticals

  • Cat’s Claw (Una de gato) has antioxidant and immune enhancing properties as well as anti-hypertensive effects (lowers blood pressure & supports circulation). Cat’s Claw is derived from a vine found in South America. It is often used in combination with other herbs. It can be useful in treating a wide variety of illness including parasites, colitis, gastritis, leaky gut, and tumors, and is also used for acute conditions such as viral and respiratory infections.

  • Chinese Herbs are available in a variety of combinations for immune support. Astragalus is one of the more commonly found Chinese herbs in immune formulations. Selecting the proper Chinese herbal formula is not always straightforward since a variety of conditions need to be considered before deciding on the best combination, so sometimes the guidance of a trained holistic veterinarian is important.

  • Green tea contains polyphenols that target cancer cells for destruction and help eliminate free radicals. Green tea also supports the production of a protein that protects healthy cells.

  • Curcumin, from turmeric root, has very powerful antioxidant and anti-inflammatory properties.  It has a wide range of uses for both chronic and acute illnesses and is an excellent cancer preventative.

  • Echinacea stimulates the immune system to fight bacterial and viral infections. It is a good choice for acute conditions, but it is not recommended for long-term use. Echinacea works best when given as a preventative to help an animal avoid contracting an illness or infection they may be exposed to. Echinacea may be contra-indicated in cancer patients, especially if they are undergoing radiation or chemotherapy.

  • Medicinal mushrooms such as Maitake, Reishi and Shiitake stimulate T-helper cells (which are integral to a strong immune response) and powerfully boost the overall immune system. Cordyceps is a Chinese mushroom with antioxidant, antiviral and cellular health boosting properties.

  • Colostrum is the first milk produced by mothers. Most colostrum commercially available is from cows. It has many immune boosting properties including factors that support T-helper cells. It may also play a role in the metabolism of essential fatty acids. Colostrum is useful for acute and chronic disease, including autoimmune disorders.

This is by no means a complete list of immune support herbs and supplements, but it includes many of the most common of those used for general immune support. Again, prevention is the best course, but should your companion fall ill, providing extra support for the immune system through nutrition, herbs, and supplements can give your pet the upper hand and aid in a speedy recovery.

Check out our immune support supplements to view our wide selection at Only Natural Pet.