Herbal Anthelmintics and Your Horse
By Patti Duffy-Salmon


There has been a lot of discussion lately about herbal dewormers and your horse. Though I feel there is still a place for chemical dewormers and your horse, I just don’t feel that chemically deworming your horse every 8 weeks is necessary.

I know that MANY of you out there will probably disagree with this statement, but being of an alternative mind, I feel that sometimes traditional practices and alternative practices can meet half way. Of course, there is ALWAYS the exception to every rule, and if your horse is having problems that could be linked to heavy worm infestations, then by all means please consult with your veterinarian and discuss a proper chemical protocol. Once a horse has reached a healthy state of existence, and has no known worm issues, and your veterinarian agrees with this statement, then it is probably safe to start incorporating herbal dewormers.

An herb classified as an anthelmintic will destroy or expel worms from the digestive system. Many of the most effective anthelmintics shouldn’t be used due in part to their high toxic properties, so care should be taken when using ANY anthelmintic herbs.

Anthelmintic herbs fall into four very different categories.

Vermifuges - herbs that expel worms from the body
Vermicides - herbs that destroy worms in the body
Taenifuges - herbs that expel TAPEWORMS from the body
Taenicides - herbs that may kill TAPEWORMS in the body

The difference between expelling and actually killing the parasites can depend on the herb used, dosage given and how often it is administered.

There are many anthelmintic herbs available, but again, due to the very toxic nature of some, I will only discuss a few of them here. These herbs should not be randomly used and fed to any animal or person unless properly mixed and prepared by a qualified herbalist. Also, most if not all of these herbs should not be given to a pregnant horse.

I think one of the most noted anthelmintics is wormwood (artemesia absinthium).

Wormwood is a pretty common perennial herb found throughout the country. Wormwood is extremely bitter due to its volatile oil, which contains absinthol or thujone. The herb also contains a bitter glycoside, absinthine, a narcotic. The oil of wormwood is extremely potent and a tiny dose can cause coma and death in an adult person. So when I refer to wormwood, I am referring to the DRIED PLANT MATERIAL and not essential oil. The essential oil is extremely concentrated and should NOT be used.

Wormwood is an excellent anthelmintic and also an effective tonic for the whole digestive system. PLEASE do not get Wormwood and Wormseed (artemisia cina or chenopodium ambrosiodies) confused with each other. Wormseed should not be ingested!

Pumpkin seeds and garlic

Pumpkin seeds and melon seeds are rich in nutrients and also help to remove large quantities of uric acid in the urine. They also contain an amino acid, cucurbitin, which gives these seeds their anthelmintic actions. Pumpkin seeds are noted for expelling tapeworms from the body. It must be noted that one should NEVER use pumpkin seeds that have been packaged for planting. These seeds have been treated with insecticides, fungicides and, sometimes, powdered fertilizers. One must never use these seeds for human or animal consumption. Use only certified organic seeds.

Hyssop (hyssopus officinalis) is another common perennial herb. The entire plant is medicinal but the most medicinal parts are the flowering tops and leaves. Hyssop’s therapeutic actions are due to its essential oil, which has anthelmintic properties.

Garlic (allium sativum) has been used as an anthelmintic for centuries. Garlic has antibacterial, antimycotic and lipid-lowering effects that have been scientifically proven over time. Garlic is extremely medicinal in many different ways.

There has been much information written lately about the possibility of garlic being toxic to horses. When fed in the proper recommended dosages, garlic is perfectly safe to feed. I have been feeding it for years with no known side effects. Over-feeding can cause gastric upset so care must be taken with the dosage. Raw garlic cloves are the most medicinal because they contain the highest amount of oil compared to dried garlic products. But most horses won’t eat whole raw cloves due in part to its extreme bitter and hot taste, so feeding garlic granules is the next best thing.


Rue (ruta graveolens) should be used with caution. In the proper dose, it is a very effective anthelmintic. Rue contains quinazoline alkaloids, quinoline alkaloids, furocoumarins and more. Rue contains a very high level of volatile oil that has been used as an abortive through the centuries. One should NEVER feed Rue to a pregnant horse.

Two herbs that should be avoided are male fern and tansy. Both have been used as anthelmintics throughout the centuries, but both are extremely toxic.

Tansy (chrysanthemun ulgate or tanacetum vulgare) is the MOST toxic of the known anthelmintics. It contains potentially harmful substances that must be used in precise dosages. It contains a very high level of the essential oil thujone and small amounts of borneol and camphor. This level of thujone has been found to be a strong uterine stimulant in both animals and humans and should never be used with pregnant animals. The essential oil is so extremely toxic that even a half-teaspoon can be fatal. Please do NOT USE this herb on yourself or your animals.

Male fern (dryopteris filix mas) is another very toxic anthelmintic. Male fern rhizomes have been used through out the ages to rid the body of tapeworms, liver flukes and other nasty parasites. Male fern can cause severe liver, cardiac and kidney damage as well as paralysis and visual disorders. The side effects and risks far OUTWEIGH any anthelmintic benefits the plant may have. Due to its MANY risks, I do not recommend any internal application of this herb. I only mention it here because it is still listed in MANY books as an anthelmintic, but not one that I would recommend at all.


I have also heard of many prescribing black walnut as an anthelmintic for horses, but I would never advocate the use of black walnut in any form to be fed to horses. The main toxic principle is juglone, which is a growth inhibitor carried in the roots and bark of the tree. Most horses show an allergic reaction to the shavings and they do not have to even ingest the material to get sick. Due to the whole allergy problem, the danger of laminitis and respiratory difficulties, and allergy related symptoms, I feel that one shouldn’t even take the chance of feeding a horse any part of the black walnut tree, be it nut, bark or root. Different products may contain different parts - some claim to use the husk of the nut, some claim to use the hull of nut, and some the bark of the tree and then some use the inner bark. No part of the black walnut is safe enough for me to recommend it.

There are several other herbs that are far safer and have anthelmintic properties. Herbs such as fennel seed, feverfew, hops, horehound, sage, southernwood and blue vervain are considered very safe to feed to your equine friend and help to deter parasites.

The use of alternative dewormers is becoming more common. Safe herbs such as those mentioned are very useful in helping to manage health and parasite problems. Consult with your veterinarian and equine herbalist to be sure you arrange the best health program for your horse.

About the author:
Patti Duffy-Salmon, owner and master herbalist of Meadowsweet Acre Herbs, Inc., specializes in custom blended herbs for horses, especially for EPM, laminitis, and Cushings, and for PMS mares. Free phone consultations, a print catalog and an on-line catalog are available. Visit Patti, her horse Moose, and Meadowsweet Acres at www.meadowherbs.com, psalmon@cafes.net, or call 931-684-8838.

Meadowsweet Acre Herbs for Horses, Inc.
Patti Duffy-Salmon
181 Wildcreek Road
Shelbyville, TN 37160