These herbs can help protect your horse from illness and infection by giving his immunity a boost.

Your horse’s immune system defends him against the toxins and pathogens that lead to illness and disease. Instead of reaching for antibiotics when your horse gets sick, take a look at how you can help him fight infections with immune-strengthening herbs from nature’s medicine cabinet.


When a foal is born, he obtains his first antibodies (which attack and destroy pathogens before they can cause disease) by drinking his mother’s colostrum. This colostrum is packed with the antibodies the mother has built up in her own body. Throughout his life, a horse will continue to build up various antibodies to the pathogens he encounters, helping to develop a strong immune response.

Unfortunately, if an animal is in poor health, rundown, malnourished, stressed, or has had his immunity weakened by chronic use of certain medications or antibiotics, his body may struggle to mount an effective defense against infection, whether viral, bacterial, protozoal or fungal. The overuse of antibiotics has played a significant role in creating antibiotic- resistant pathogens. These pathogens have learned to adapt and mutate in order to overcome destruction by antibiotics.


Herbal medicine has much to offer in this respect, because medicinal herbs possess a variety of actions — antibiotic, antifungal, antiviral, antiseptic and antiprotozoal. Medicinal herbs can be regarded as “active” medicines. They contain multiple constituents, giving them actions that pathogens are unable to “read” the same way they do the isolated chemicals in conventional antibiotics. Herbal medicine is infinitely adaptive — because herbs each have such a broad range of active constituents, they can “multi-task”, helping the horse’s immune system respond to attack in a variety of ways.


1. Anti-infective, antimicrobial, antifungal, antiseptic, antiprotozoal

These plants have active constituents that are destructive to harmful bacteria, fungus or protozoa.

Garlic (Allium sativum) — Garlic is antifungal, antibacterial, antiparasitic, antiviral, and immune-enhancing. It contains volatile oil compounds thought to be responsible for most of the herb’s properties. Garlic was used widely as an antiseptic before the discovery of modern antibiotics, and was the main course of treatment for preventing gangrene in the trenches during the two World Wars. Its antiseptic action was subsequently confirmed in modern clinical studies, which showed it will inhibit the growth of Staphylococcus, Streptococcus, Bacillus, Brucella, E. coli, Salmonella, Klebsiella and Mycobacteria. Studies have also confirmed garlic’s antibacterial effects and have demonstrated that it can effectively inhibit the growth of some of the bacterial strains that have become resistant to modern antibiotics!

Garlic has also been shown to inhibit the growth of Candida albicans and to be more effective as an antifungal than orthodox antifungal preparations.

herbsBurdock (Arctium lappa) — This plant is known as the “power digger” of the herb
world because of its ability to remove toxins from cells and encourage their removal from the body. It is particularly effective for skin conditions, septic disorders, and any chronic inflammatory condition. Burdock is absolutely safe to use long-term, and combines particularly well with garlic for any chronic infective condition.

Marigold (Calendula officinalis) — Marigold is antibacterial, antiviral, antifungal, antiprotozoal and immune-stimulatory. All these actions have been confirmed by research in which tinctures of calendula showed activity against E. coli, Staph aureus and Strep feacali. The antiviral and antiprotozoal action comes from the resins and volatile oil contained in the plant, while the antibacterial action is due to marigold’s water-soluble glycoside constituents. Calendula is known as the supreme herb for the skin, and can be used either internally or topically as an oil, decoction, compress or tincture.

Eyebright (Euphrasia officinalis) — Containing the glycoside aucubin (as does plantain), this herb has been shown to have antiseptic action on the mucous membranes of the upper respiratory tract. When used externally as an eyebath or compress, it can help control eye infections and ulceration.

To make an eyebath, put approximately 3 g of dried eyebright and 100 ml of water in a small saucepan. Cover with a lid, bring to a boil, then simmer gently with the lid on for three to five minutes. Allow to cool, then strain. The strained liquid (tea) can be stored in an airtight sterilized container in the refrigerator for up to two days. Don’t waste the herb you have used to make the tea — just add it to your horse’s food.

Thyme (Thymus vulgaris) — Thyme is both an astringent and disinfectant. It contains thymol, which is antibacterial, antiviral, antiparasitic, antifungal and antiseptic. It can be used both internally and externally. Thyme is excellent when used as an antiseptic expectorant for the respiratory system, and as a disinfectant for the urinary system. Externally, it can be used for bathing wounds and as a skin wash.

2. Alternatives, depuratives, detoxers

These plants contain constituents that, rather than having a direct effect on pathogens (although some do), support and restore the normal functions of the affected organ or system, helping to remove toxic waste and improve overall immunity and resistance to infection.

Kidneys and urinary system — dandelion leaf, couch grass, bearberry (Uva ursi), celery seed, horseradish

Liver — milk thistle, dandelion root, yellow dock Lymphatic system — cleaver, poke root, marigold, Echinacea, burdock

Respiratory system — garlic, elecampane, thyme, liquorice, plantain, horseradish

Skin — cleaver, marigold, burdock, red clover, yellow dock

Digestive system — goldenseal, sarsaparilla


3. Adaptogens

Adaptogens have been shown to help the body “adapt” and mobilise its own defence systems to reduce the effects of stress, which can contribute to depleting the immune system. They involve the action of the whole plant rather than individual constituents, which can affect different types of cells. Adaptogens exert influence on many different types of cells in the body — this contrasts to chemical drugs which tend to have a direct action on particular tissues or systems. Adaptogens include gotu kola, Siberian ginseng, don quai, borage, sarsaparilla, withania, and various medicinal mushrooms.

4. Immune activators, stimulants, modulators

These plants don’t target specific pathogens, but work by strengthening non-specific immunity; they do this by stimulating and enhancing the body’s overall immune response. The body’s natural resistance to infection is boosted by the increased production of cells responsible for attacking bacteria and invading pathogens.

Plantain (Plantago major) — This plant contains polysaccharides, which increase phagocytosis (the immune cells responsible for removing pathogens from the body), producing an immune-stimulating action.

Purple coneflower (Echinacea spp. purpurea, angustifolia, pallida) — No article on immunity would be complete without mentioning Echinacea! This herb has immune-modulating, antimicrobial, antiseptic and antibiotic effects. Knowledge about the use of Echinacea first came from the Native Americans, who used it for varied conditions such
as snakebite, septic wounds, syphilis, typhus, dysentery, and even cancer. It is generally accepted that the plant’s antibacterial and antiviral activities result from the individual’s enhanced immunity.

Both the aerial parts and the roots are used in herbal medicine, although my personal preference is to use the roots of Echinacea purpurea. This plant is particularly effective for any upper respiratory tract infection such as colds or flu, and I have used it with great success for horses with URT infection. Echinacea has been the subject of a great deal of research, much of which confirms its immune-modulatory action. This action can increase phagocytosis while also stimulating the production of lymphocytes, including natural killer cells, T cells and B cells, all of which are found in the lymph and are responsible for the body’s cell-mediated immune response. Extracts from the roots of various Echinacea species have been shown to have an antiviral effect against the herpes simple and influenza virus.

Pau d’arco (Tabebuia spp) — This herb is immuno-stimulating, anti-tumor, antimicrobial, antiparasitic, antiviral and depurative. The inner bark of the tree contains lapachol, which is thought to possess significant immune-enhancing and anti-tumor activities.

Pau d’arco tincture can be used internally for digestive infections, and topically for skin diseases, fungal infections such as ringworm, and Candida albicans. It should be noted, however, that because of the bark’s napathaquinone content (which has a warfarin-like action), this herb is contraindicated for individuals on anti-coagulants.

Hopefully, this foray into the wonderful and powerful world of herbal medicine has given you some insight into how something as simple as a plant can have a prolonged and dramatic effect on something as complex as immunity!



Hilary Self is cofounder of Hilton Herbs Ltd., a company that manufactures and formulates herbal supplements for animals. She is a Medical Herbalist, a member of the National Institute of Medical Herbalists, and a member of the NASC Scientific Advisory Committee. Hilary is the author of two books: A Modern Horse Herbal and A Veteran Horse Herbal. HiltonHerbs.com