Do Natural Dewormers Really Work?

Parasite control is a hot topic among livestock producers, homesteaders and veterinarians. As a veterinarian, gastrointestinal worms are the top killer I find in our sheep and goat populations—especially in the Southeastern United States where my flock lives. Staying two steps ahead in the war against parasites is an uphill battle. And unfortunately, the deworming medications we have at hand are losing their firepower.

A quick Google search for ‘natural dewormers’ will lead you down all kinds of rabbit holes… you’ll find recipes for herbal blends, vinegar treatments, mixtures of essential oils and maybe even stranger potions. Some of the advice online is credible, but much is absolute quackery.

Before you stone the big, bad, drug-toting veterinarian, hear me out! There has been some exciting research into the world of non-pharmaceutical control of endoparasites in small ruminants! I’m not here to sell you drugs! Let’s look at some worthwhile alternatives to traditional dewormers.

I’m asked all the time whether XYZ holistic mix will work against worms. And the short answer to most inquiries is: maybe, but not as a stand-alone replacement for smart, targeted parasite management.  More tools are better than less, but we’ve got to be strategic when drawing from our arsenal.

Here’s the reality: worms are survivalists. They’ve been adapting to chemical dewormers for decades, and they can just as easily adapt to overused herbal remedies. Whether you’re using ivermectin or a mason jar of “all-natural” brew, if you blanket-treat your entire herd on a regular schedule, you’re training the parasites to outsmart you.

Selective deworming is the gold standard, whether your tools are pharmaceutical or herbal. That means identifying and treating only the animals that are noticeably struggling under their parasite load — those showing poor body condition, rough coats, diarrhea, anemia, or low FAMACHA scores.  We must purposefully leave healthier animals untreated so susceptible worms stay in the population. This approach slows resistance, saves money, and spares your animals unnecessary interventions.

What About ‘Natural’ or Herbal Dewormers?

When people say ‘natural dewormer,’ they’re usually talking about plants or plant-derived products — garlic, pumpkin seeds, papaya seeds, wormwood, clove, black walnut hulls, and a variety of proprietary herbal blends. The problem is, while many of these have been studied in vitro, in a petri dish.  That’s not the same as proving they work in vivo, in a live animal at realistic doses. 

The usefulness of some medicinal plants is limited by how much an animal would have to consume to see results.  If a sheep needs to 100+ pounds worth of a plant in one sitting to achieve therapeutic levels, obviously that is not anatomically possible. 

We are also limited by the animal’s appetite and palate.  Some herbs smell and taste terrible, so your goats won’t eat them voluntarily (so we’re back to square one of needing to individually dose). 

And lastly, in some plants the margin between therapeutic and toxic is extremely small, so poisoning is possible.  Too much of a good thing can be catastrophic.

So Which Medicinal Plants Show Promise?

Here’s what veterinary research actually shows:

Condensed tannin forages (sericea lespedeza, birdsfoot trefoil)

These legumes contain plant compounds called condensed tannins, which have been shown in multiple studies to reduce fecal egg counts and improve packed cell volume (anemia status) in sheep and goats. They don’t “cure” heavy infections, but they could be a valuable part of an integrated parasite control program.

Ironically (and unfortunately), both serica lespedeza and birdsfoot trefoil are extremely invasive weeds that will outcompete and kill other forages and grass.  Hay producers work hard to keep these plants out of their fields.

Wormwood (Artemisia absinthium) & related Artemisia species:

Some lab studies suggest anti-parasitic effects, but results in live animals are inconsistent. Also, safe dosing is tricky — too much can be toxic.  This perennial shrub contains thujone, a chemical that can cause seizures.  This plant may be best left to its most common human use, an ingredient in the alcohols absinthe and vermouth.

Myth: ‘Natural means safe.’
Fact: Many plants used as herbal dewormers can cause toxicity, organ damage, or anemia at high doses.

Pumpkin seeds

Pumpkin seeds have shown promise against certain parasites in other animal species and are an age-old remedy in human folk medicine.  That said, data in sheep and goats is extremely limited.  Pumpkin seeds are unlikely to control a heavy Haemonchus burden on their own.  And the number of seeds needed to make a dent is likely on par with the volume that could cause a GI impaction.  I’ll be interested to see whether future studies on pumpkin seed extracts earn this festive gourd a spot on the proven dewormer roster.

What About Copper Oxide Wire Particles (COWP)?

Research shows that copper oxide wire particles can reduce Haemonchus contortus (barber pole worm) burdens in sheep and goats, with the best efficacy when used alongside anthelmintic drugs rather than as a sole treatment.  However, copper is an essential trace mineral with a very narrow safety margin in sheep.  Read that again.  By narrow I mean very very thin, super skinny, no-wiggle-room! Overdosing—even slightly—can lead to copper toxicity, which causes liver damage, jaundice, and death.

Goats tolerate more copper than sheep, but dosing precision is still critical. Sheep are especially vulnerable because toxic thresholds are low (often 15–20 mg/kg body weight), and copper accumulates in the liver over time. If COWP is used, it should be part of a meticulously calculated, veterinarian-guided parasite control program that accounts for diet, mineral supplementation, and species-specific tolerance.

Quack Quack! These Remedies Don’t Work:

Garlic (Allium sativum)

Despite its popularity in internet recipes, the evidence in small ruminants is weak. Some studies show minor reductions in egg counts, others show no measurable effect. At higher doses, garlic can cause anemia itself — the last thing a parasite-ridden animal needs. Feeding garlic to a parasite-ridden animal may actually make its condition worse.

Apple Cider Vinegar (ACV)

Don’t come for me, internet pitchforks, I’m just stating facts. 

Even though apple cider vinegar is a homestead favorite … my advice is to limit its use to cooking.  Most “cures” are anecdotal at best and detrimental at worst.  ACV does nothing to treat parasites.  Of any variety. Evidence simply doesn’t support that claim that it can be used to deworm any species.  Useless for sheep, goats, dogs, cats, pigs, cattle and poultry.

Take Home Message

Herbal remedies are not automatically safer, more effective, or more sustainable than drugs — they’re just another tool. The difference is that most haven’t been rigorously tested, dosing isn’t standardized, and the margin between “helpful” and “harmful” can be thin. Using them without understanding those limits risky.  But working with your veterinarian to create a multi-modal parasite control program is a worthwhile investment.

So, before you reach for that ‘miracle mix’ you found online, remember: the enemy is the worm, not the tool.   Use whatever works, but use it strategically, selectively, and backed by science.  And again, reach out to your local livestock veterinarian for help.  Your own farm doc can help you develop a plan to selectively treat your critters, and keep them healthy, happy and ahead of those pesky parasites!

For My Fellow Plant Nerds