Natural Equine Support: The Best Herbs for Horses

Walk into almost any UK feed room and you will find herbs for horses in some form: a tub of devil’s claw for an older horse’s joints, garlic granules in summer, a calmer built on valerian or chamomile, a bag of cleavers and marigold. A few of these herbs have been studied in horses. Most have tradition, a good label and very little else behind them. This guide goes herb by herb through what equine research has actually found, which herbs are banned or controlled on the FEI’s 2026 prohibited list, what UK rules allow a herb label to claim, and how to feed herbs without doing harm.

What Are Herbs for Horses?

In feed-room terms, a herb is any plant fed for something other than bulk energy: dried leaves, flowers, roots, seeds or berries, sold as a single “straight” or mixed into a blend. Horses already eat plenty of them without anyone planning it. Old permanent pasture carries a mix of grasses and broad-leaved herbs, and so does the meadow hay cut from it, while some bagged chaffs now come with dried herbs mixed in.

What sets a herb apart from grass is its chemistry. Many contain compounds with a measurable effect on the body: harpagoside in devil’s claw, curcumin in turmeric, silibinin in milk thistle, valerenic acid in valerian and salicylates in meadowsweet and willow bark. That chemistry is the reason owners feed them, and it is also why several of those compounds appear on the FEI’s prohibited list. A plant that can change how a horse feels can change how it performs.

The research base is thin. Reviewing commonly fed herbs for The Veterinary Journal in 2008, Williams and Lamprecht of Rutgers University put it plainly: “Most herbs and functional foods have not been scientifically tested; this is especially true for the horse.” They added that few studies have investigated safe, effective doses, that some herbs contain prohibited substances such as salicylates and digitalis, and that drug-herb interactions are common (PMID 17689992). The picture has improved since then, but only in patches, and the sections below say exactly where.

Herbs for Horses at a Glance: What the Evidence Says

The table summarises the best equine evidence we could find for each herb on PubMed, the US National Library of Medicine’s research database, in September 2026, alongside its status on the FEI 2026 Equine Prohibited Substances List. “Not named” means the herb’s main compound does not appear on the list by name. That is not a clearance: the list itself says prohibited substances “include any other substance with a similar chemical structure or similar biological effect(s)”.

The Best-Known Herbs for Horses, One by One

These are the herbs UK owners search for most, roughly in order of search interest, with what the research says and what to watch for.

Devil’s Claw for Horses

Devil’s claw (Harpagophytum procumbens) grows in the Kalahari region of southern Africa, where it is used traditionally for arthritis, pain and fever. A 2012 review from the Tshwane University of Technology in Pretoria notes that Namibia is the main exporter, that only the secondary tubers are used commercially, and that stock is often adulterated with a close relative, H. zeyheri, which carries less of the active compounds (Mncwangi et al., Journal of Ethnopharmacology, PMID 22940241). For horses it is sold mainly as a joint herb for older or stiff animals.

The equine research is about how the body handles it, not whether it works. Axmann and colleagues at the University of Veterinary Medicine, Vienna, gave six horses devil’s claw extract by stomach tube and could detect harpagoside, its main active constituent, in the blood for up to nine hours, with no clinically detectable side effects (Journal of Veterinary Pharmacology and Therapeutics 2019, PMC7379497). The authors describe devil’s claw as used in horses “since many years, but without the substantive pharmacokinetic data”. A PubMed search in September 2026 returned no controlled trial of devil’s claw on lameness in horses.

Two cautions matter more than the marketing. First, harpagoside is listed as Controlled Medication on the FEI’s 2026 list, and a French racing laboratory has published methods built specifically to find devil’s claw compounds in horse urine and plasma (Colas et al., Rapid Communications in Mass Spectrometry 2006, PMID 17044124). Second, the human evidence points at the stomach. The drug bulletin Prescrire has reported cases of gastrointestinal bleeding linked to devil’s claw root, and a review of about 20 placebo-controlled human trials in which the side effects were mainly stomach pain and indigestion (Prescrire International 2013, PMID 24600731). There is no equine data either way, so if your horse has had gastric ulcers, talk to your vet before starting it.

Be wary of the label as well as the herb. The Veterinary Medicines Directorate gives “The herbal alternative to phenylbutazone (Bute)” as an example of a claim a non-medicinal product must not make (see what a herb label can legally say). A stiff horse needs a diagnosis, and our guides to lameness and arthritis in horses cover what your vet will look for.

Turmeric

Turmeric is fed for its curcumin, and most of what is known about it in horses comes from the laboratory. At the University of Nottingham, Clutterbuck and colleagues exposed cartilage from eight horses to an inflammatory signal; curcumin at the highest concentration tested reduced the release of cartilage components by an average of 20% and 27% at the two inflammatory doses used (Annals of the New York Academy of Sciences 2009, PMID 19723086). That is cartilage in a dish, not a horse eating turmeric.

In live horses, an Italian placebo-controlled study fed 16 show jumping horses a commercial blend of boswellia, mullein and turmeric for ten days and found lower expression of several pro-inflammatory genes, but no effect on the horses’ antioxidant defences (Beghelli et al., Life 2023, PMC10055707). Because it was a blend, the result cannot be pinned on turmeric. A curcumin additive also failed as a natural wormer (see garlic below). Turmeric is not named on the FEI list. For feeding and product choice, see our full guide to turmeric for horses.

Milk Thistle for Horses

Milk thistle (Silybum marianum) is fed for the liver. Its best equine data come from Colorado State University, where Hackett and colleagues gave nine healthy horses silibinin, a milk thistle derivative, in a phospholipid-complexed form. Only 0.6% of the dose reached the bloodstream when it was eaten in feed, and 2.9% when it was given by stomach tube. It did not build up with twice-daily dosing for a week, there was no dose-limiting toxicity at the doses tested, and plasma antioxidant capacity rose as the dose went up (American Journal of Veterinary Research 2013, PMIDs 24066917 and 24066918). The authors’ own conclusion: safe, “although poorly bio-available”, with further study needed in horses that actually have liver disease.

A Czech study fed milk thistle seed cake to 12 Czech Warmbloods in combined driving and found differences in plasma cortisol and non-esterified fatty acids after hard exercise, compared with controls (Dockalova et al., Journal of Equine Veterinary Science 2022, PMID 35318098). Interesting, but it tells you nothing about a horse with a damaged liver.

That is the gap that matters. Liver disease in horses has causes that need finding, from ragwort poisoning to viral hepatitis, and none of them is a job for a supplement bought on spec. Your vet may still suggest milk thistle as part of supportive care once the cause is known, but the diagnosis comes first. Milk thistle is not named on the FEI list.

Valerian for Horses

Valerian root is the classic herbal calmer, and it is a herb to keep well away from any competition horse. The British Equestrian Trade Association (BETA) names valerian as the source of valerenic acid, and valerenic acid is listed as Controlled Medication (sedative) on the FEI’s 2026 list, with the same status on the 2027 list the FEI has already published. The FEI defines Controlled Medication as substances with “therapeutic value” that “have the potential to affect performance”, and its list covers every substance “prohibited for use during FEI events” (FEI prohibited substances page). BETA’s own code allows valerian only in products for horses not competing.

Whether valerian calms a horse at all is unanswered: our PubMed search found no controlled equine trial of valerian on behaviour. What does exist is a small survey of 58 horse owners in the north of Scotland. Of those who had used a calming product, 40% felt it had some positive effect, 30% were unsure, 25% saw no difference and 5% felt it made behaviour worse. Among respondents, 59% thought the active ingredient was magnesium, 9% named herbs, valerian or tryptophan, and 32% did not know (Ross and Roberts, Journal of Equine Veterinary Science 2018, PMID 31256891). The authors concluded that owners use calmers “without underpinning knowledge of ingredients or scientific evidence of efficacy”.

Garlic for Horses

Garlic is fed for fly and midge control, for coughs and for general health, and it is the herb with the clearest equine safety signal. At the University of Guelph, Pearson and colleagues fed freeze-dried garlic in molasses to two horses, with two controls, raising the amount over 41 days until the horses would eat no more and feeding it for 71 days in total. At more than 0.2 g of garlic per kg of bodyweight a day, the garlic-fed horses developed Heinz body anaemia, in which red blood cells are damaged and broken down. Blood values had largely recovered five weeks after the garlic stopped, though some markers were still raised (American Journal of Veterinary Research 2005, PMID 15822591).

Read that finding carefully. The paper did not set a safe dose (“further study is required to determine the safe dietary dose of garlic in horses”), and its headline is that horses “will voluntarily consume sufficient quantities of garlic to cause Heinz body anemia”. So 0.2 g per kg a day, which works out at 100 g of dried garlic a day for a 500 kg horse, is where harm was seen, not a line below which garlic is safe. Heinz body anaemia is also a different disease from iron-deficiency anaemia: the red cells are made and then destroyed, so an iron supplement will not fix it.

The benefits are much less certain than the risk. We found no controlled equine study of garlic as a fly or midge repellent. As a wormer, garlic failed the only controlled equine trial we found. At the University of Naples Federico II, Buono and colleagues gave 15 naturally infected mares 40 g a day of fresh or dried garlic, or nothing, for 15 days, and garlic did not reduce worm egg shedding (Journal of Equine Veterinary Science 2019, PMID 30929787). Other plant-based alternatives have failed too. At INRAE in France, Malsa and colleagues fed commercial additives based on mugwort, echinacea or curcumin to 18 naturally infected Welsh ponies, with six untreated ponies as controls. None had a significant effect, no additive cut worm egg counts by more than 38.6% against the controls, and the authors concluded the results “do not support the practical use of these additives” (Journal of Equine Veterinary Science 2024, PMID 39299557). Worm control belongs with faecal egg counts and your vet, as set out in the BHS guide to risk-based worm control and our worming guide.

Echinacea for Horses

Echinacea is a common ingredient in “immune” blends, and it has one of the better equine trials. O’Neill, McKee and Clarke at the Equine Research Centre in Guelph ran a double-blind, placebo-controlled crossover trial in eight healthy horses fed a standardised Echinacea angustifolia extract for 42 days. The extract increased the phagocytic (engulfing) ability of neutrophils, raised lymphocyte counts, and increased red cell size and concentration, haemoglobin and packed cell volume (Equine Veterinary Journal 2002, PMID 12108738).

Those are blood measurements in healthy horses over six weeks. The trial did not test whether echinacea-fed horses caught fewer infections or recovered faster, and our PubMed search found no later equine trial that did. In the INRAE worm trial above, an echinacea additive had no significant effect on worm egg counts. It is also why echinacea tubs in the UK say “supports” rather than “boosts”: the Veterinary Medicines Directorate gives “Boosts the immune system” as an example of a claim a non-medicinal product must not make. Echinacea is not named on the FEI list.

Chamomile, Lavender and Other Calming Herbs

Chamomile, lemon balm and passionflower are familiar names on herbal calmer labels. The equine evidence for feeding them is close to nil: our PubMed search found no controlled trial of chamomile fed to horses. The one relevant study tested scent. At the University of Arizona, Baldwin and Chea had eight dressage horses breathe humidified essential oil while their heart-rate variability was recorded. Lavender produced a short-lived rise in the parasympathetic (rest-and-digest) measure immediately after the session; chamomile’s effects were variable and none reached significance (Journal of Equine Veterinary Science 2018, PMID 31256887). So if you have wondered what smell calms horses, lavender has one small study behind it, and chamomile did not show an effect in the same study.

Before any calmer, look for the cause. As Horse & Hound’s guide to herbal remedies puts it: “If your horse is uptight because a badly-fitting bit is causing him discomfort, you can’t expect a herbal calmer to put things right.” Check pain, diet, turnout and handling before reaching for a tub. When a horse genuinely needs calming for clipping, shoeing or travel, vets use prescription sedatives such as xylazine, chosen and dosed for that horse and that job. Kava (Piper methysticum) is listed as Banned on the FEI list, meaning it is not permitted in a competition horse at any time.

Sea Buckthorn

Sea buckthorn berries turn up in stomach supplements, and they have a proper trial behind them. At Louisiana State University, Huff and colleagues fed a commercial sea buckthorn berry and pulp emulsion to eight Thoroughbred and Thoroughbred-cross horses for four weeks, then withheld feed intermittently for a week to provoke ulcers, and compared the results with the same horses untreated. The product made no difference to ulcers in the non-glandular (squamous) part of the stomach, but glandular ulcer number and severity were significantly lower in treated horses at week five (Journal of Veterinary Internal Medicine 2012, PMID 22845737).

The authors’ conclusion is that sea buckthorn “might have efficacy in prevention of glandular ulcers” in stabled horses on intermittent feeding. It is not a treatment for ulcers a horse already has. Ulcers are diagnosed by gastroscopy and treated by your vet, and our guide to ulcers in horses and the EGUS entry explain both types.

Meadowsweet and Willow Bark

Meadowsweet and willow bark are sold for their salicylates, the same chemical family as aspirin. That is exactly the problem for competition horses. Salicylic acid is listed as Controlled Medication on the FEI’s 2026 list and has a published threshold (the FEI’s threshold list is on its prohibited substances page), and BETA names willow bark and meadowsweet as its typical sources. We found no controlled equine trial of either herb for pain. A horse sore enough to need pain relief needs a vet and a licensed drug, not a hedgerow version of one.

Agnus Castus (Chasteberry)

Agnus castus, or chasteberry, is sold for older horses with PPID (Cushing’s) and for moody mares. For PPID the question has been answered. The British Equine Veterinary Association’s primary care guidelines, drawn up by a panel including vets from the Royal Veterinary College and the University of Liverpool and graded on the GRADE framework, state that “chasteberry has no effect on ACTH concentrations and there is no benefit to adding chasteberry to pergolide therapy”, while pergolide “improves most clinical signs associated with PPID in the majority of affected animals” (Menzies-Gow et al., Equine Veterinary Journal 2024, PMID 37795557). If you suspect PPID, see our guide to Cushing’s disease in horses and ask your vet about testing. For mares, our guide to mares in season covers the options.

Mint, Nettle, Rosehip and the Everyday Forage Herbs

Some herbs are fed less as remedies than as tasty, familiar forage: mint, nettle, dandelion, yarrow, rosehips, and the cleavers-and-marigold mixes sold by several UK suppliers. There is little research on them as treatments, but there is some on whether horses will eat them. At the University of Life Sciences in Lublin, Stachurska and colleagues offered 20 adult horses oats with field mint, yarrow, chamomile, sage or nettle added. The herbs did not put the horses off; only the smell of dry sage delayed eating, and wetting or sweetening the feed sped it up. Their conclusion: “herbs in small amounts do not significantly affect the willingness to consume feed” (Animals 2022, PMC9179354).

Rosehips are sold mainly for their vitamin content, and we found no equine study of feeding them. None of these herbs is named on the FEI list. That tells you about competition rules, not about benefit.

Thyme, Oregano and Rosemary: the “Oily Herbs”

Dried thyme, oregano and rosemary, often called oily herbs, have become a forum favourite, with owners mixing their own blends. The nearest research is on terpenes, the class of aromatic compounds that gives these herbs their smell. In a 2026 French and Danish study, the terpenes carvacrol and cinnamaldehyde were highly active against small redworm (cyathostomin) larvae in the laboratory and had anti-inflammatory effects on equine immune cells, but when cinnamaldehyde was fed to horses for 28 days it had no effect on worm egg output or blood cell profiles. The authors describe a gap “between in vitro properties and in vivo efficacy” (Malsa et al., International Journal for Parasitology: Drugs and Drug Resistance 2026, PMC13101707). Thyme is sold as a straight herb for horses by UK suppliers and is not named on the FEI list, but we found no equine study of its safety or effect when fed.

Herbs and Competition: The FEI List and BETA NOPS

If your horse competes under FEI rules, the herb question is a legal one before it is a health one. The FEI sets out its position in three public documents:

• The 2026 Equine Prohibited Substances List. It names compounds rather than plants, and states that prohibited substances “include any other substance with a similar chemical structure or similar biological effect(s)”. Banned Substances are “not permitted for use in the competition horse at any time”; Controlled Medication is prohibited during FEI events.
• The FEI’s warning on supplements, which says “it is not unusual for supplements, herbal remedies etc. marketed within the equine industry or over the internet to contain Banned Substances or Controlled Medication Substances that are not disclosed on the product label”, and that “a contaminated supplement will not excuse a positive doping test”.
• Its FAQ for athletes, grooms and support personnel, which says the constituent components of all herbs and essential oils must be checked against the list, and that the FEI does not check individual feeds or supplements for you.

These are the plant-derived substances on the 2026 list that matter most to herb feeders. The plant-to-substance pairings come from BETA’s NOPS list, except kava, which the FEI lists by name, and capsaicin, the compound that makes chilli hot. We checked every one against the 2027 list the FEI has already published, and none changes status.

Blends can carry surprises. In a 2026 study at Texas A&M, 40 horses fed a commercial herbal blend containing milk thistle, bacopa, ashwagandha, green tea and turmeric for 56 days showed a dose-dependent rise in plasma caffeine, while the antioxidant and inflammatory measures the blend was meant to improve did not change (Semanchik et al., Journal of Animal Science 2026, PMC12918311). Caffeine is Controlled Medication on the FEI list.

For UK owners the practical tool is the BETA NOPS Code (naturally occurring prohibited substances), set up in 2009 and now run solely by the British Equestrian Trade Association. It added a list of herbal NOPS in 2016 and splits them in two:

• High priority, not permitted in equine feed or supplements: cathine (khat), digitoxin (foxglove), ephedrine (ephedra), reserpine (Indian snakeroot) and synephrine (bitter orange).
• Low priority, permitted but only for horses not competing: harpagosides (devil’s claw), salicylic acid (willow bark, meadowsweet), valerenic acid (valerian) and yohimbine. Products that deliberately contain these must say so on the pack together with an indication of a withdrawal period, and may not carry the NOPS logo.

The scheme certifies companies rather than single products, and BETA runs a NOPS webchecker from its feed safety page so you can check a supplier. If you compete, buy from certified companies, read the pack for any withdrawal indication and follow it, and do what the FEI recommends: keep a logbook of every supplement with the date, dose, place, official product name and batch number. The FEI’s own summary is blunt: “IF IN ANY DOUBT, DO NOT GIVE IT TO YOUR HORSE.”

National competition and racing have their own rules. This guide quotes the FEI list because it is published in full; if you compete nationally in the UK or South Africa, or race, check your own governing body’s rules as well.

What a Herb Label Can Legally Say in the UK

Ever wondered why a herb tub “supports healthy joints” rather than treating arthritis? UK rules are the reason. The Veterinary Medicines Directorate’s guidance on advertising non-medicinal veterinary products, last updated on 25 September 2026, applies to feeds, supplements and calmers. A product presented as treating or preventing disease needs authorisation as a veterinary medicine before it can be sold, and the VMD is explicit: “Herbal products, nutraceuticals and ‘natural’ products follow the same rules as other products. A natural origin provides no exemption.”

Unauthorised products may only be presented for maintaining health in healthy animals, and the VMD treats “support” the same way as “maintain”. Its examples of claims these products must not make include “Boosts the immune system”, “Reduces pain” and “The herbal alternative to phenylbutazone (Bute)”. Saying a product “may help” does not get round the rule, neither does a disclaimer, and sellers must not refer to a herb’s traditional medicinal use.

For owners, that is a useful filter. A herb sold as a feed has not been assessed as a medicine, and a product whose marketing promises to treat a condition is either an authorised medicine, which will say so, or outside the rules. Either way, a horse with a condition needs a diagnosis first.

Herbs That Are Not Safe for Horses

“Natural” says where a product came from, not what it does. Richard Cleeve of Natural Animal Feeds, quoted in the same Horse & Hound piece, made the point years ago: “You’ve got to be just as careful with herbs as with anything else.” These are the herbs and herb-related risks to keep out of the feed room.

• Comfrey. Comfrey still turns up in some dried joint blends, but it contains dehydropyrrolizidine alkaloids, which can damage the liver. A team at the US Department of Agriculture’s Poisonous Plant Research Laboratory notes that regulatory agencies and international health organisations have recommended it for external use only (Brown et al., Journal of Applied Toxicology 2016, PMID 26177929). Pyrrolizidine alkaloids are the same class of toxin that makes ragwort poisoning so dangerous.
• St John’s wort. Hypericum perforatum is one of the main plants behind primary photosensitisation in grazing livestock, where plant compounds activated by light damage the skin (Péli and Cserhalmi, Veterinary Sciences 2026, PMC13030745). Do not feed it, and pull it from paddocks.
• Contaminated herb feeds. Researchers in Leipzig tested 48 compound horse feeds containing alfalfa or herb blends for pyrrolizidine alkaloids and found quantifiable levels in 41. The highest readings were in two alfalfa-based feeds and one herb-containing feed, and 43% of samples exceeded the maximum tolerable level the authors calculated, although they note that horses’ own susceptibility is unknown (Rückert et al., Equine Veterinary Journal 2019, PMID 30353948). Ask your supplier how its herbs are sourced and tested.
• Garlic in quantity. Covered above: Heinz body anaemia at more than 0.2 g per kg of bodyweight a day, with no safe dose established.
• Foraged plants you cannot name. Foxglove is common in the hedgerows and woodland edges where people pick “hedgerow herbs”. Our guides to plants poisonous to horses and trees toxic to horses show what to look for. If you are not certain what a plant is, do not feed it.

Herbs can also interact with medicines, and Williams and Lamprecht’s review called drug-herb interactions “common”. Tell your vet about every herb your horse eats, and ask before feeding any herb to an in-foal broodmare, a youngster, or a horse with liver, kidney or stomach trouble.

Growing Herbs for Horses

Planting herbs along a fence line or a track system is a popular way to add variety, and dried “hedgerow herbs” mixes sell the bagged equivalent. A border commonly includes mint, chamomile, thyme, yarrow, calendula (marigold), dandelion and nettle, with hawthorn and dog rose in the hedge. A few practical points:

• Plant behind a fence or mesh so horses browse the tips rather than pull up the roots.
• Identify every plant with certainty, and check the border and the surrounding paddock for ragwort, foxglove and St John’s wort through the season. Our guide to removing ragwort covers clearing it safely, and our paddock care guide covers the rest of the field.
• Never tip garden cuttings over the fence. Garden waste thrown into a field is one of the commonest routes to poisoning, as our poisonous plants guide explains.
• Do not rely on “self-selection”. The idea that horses pick out the herbs they need is popular, but we found no controlled study showing it, and horses will eat harmful plants when grass runs short.

How to Feed Herbs to Horses Safely

1. Start with the problem, not the herb. Stiffness, poor condition, coughing and tension all have causes a vet can find, and several need treatment no herb can give. Many feeding problems are better solved by getting the basic ration right, as our horse feeding guide explains.
2. Introduce one herb at a time, in a small amount, building up gradually so you can see how your horse responds.
3. Stick to the manufacturer’s feeding rate. Few herbs have tested equine doses, and the garlic study above showed horses will happily eat enough of a herb to harm themselves.
4. Tell your vet what you feed, especially if your horse is on medication.
5. If you compete, check every ingredient against the FEI list, buy from BETA NOPS-certified companies, and keep a logbook with batch numbers.
6. Be sceptical of treatment claims. A product promising to cure a condition is either a licensed medicine or outside UK rules.
7. Store dried herbs sealed, cool and dry, and throw out anything musty or mouldy.
8. Stop and call your vet if your horse goes off its feed, loses condition, develops loose droppings, or gets sore skin in sunlight after starting a new herb.

When a Herb Is the Wrong Answer

Most herbs are bought to fix something. These are the problems where the fix lies elsewhere, each with its own guide in our horse care section:

• Stiffness and lameness: a lameness work-up and a management plan (lameness in horses, arthritis).
• Weight gain and laminitis risk: diet and exercise, not a “metabolic” herb (equine obesity, laminitis).
• Coughing: dust control and a diagnosis (heaves, coughing in horses).
• Worms: faecal egg counts and targeted treatment (worm infestations).
• Stomach pain or poor appetite: gastroscopy and treatment (ulcers in horses).
• PPID: testing and pergolide (Cushing’s disease).
• Liver disease: a diagnosis first (ragwort poisoning, viral hepatitis).

Frequently Asked Questions