Everything You Should Know About Yarrow

Yarrow (Achillea millefolium) is a flowering perennial that grows in North America, Asia, and Europe. It has a rich history as one of the oldest plants used medicinally, with reports of its use dating back 3,000 years.

In test tube studies, yarrow’s active ingredients have been shown to work as antibiotics, antioxidants, antiproliferatives (slowing cell growth), and more. These properties make yarrow a supplement of interest for almost everything from multiple sclerosis to cancer.

This article explores yarrow's potential uses and benefits, as well as possible side effects and precautions.

Uses of Yarrow

Although yarrow has been used traditionally in many cultures for many health conditions, only weak evidence exists to confirm the plant's benefits. Most scientific research has been performed on animals or isolated cells in a lab. This means research is in its early stages. The findings must be replicated in more extensive and in-depth studies before the yarrow's complete safety and benefit profile is established.

The U.S. Food and Drug Administration (FDA) has approved the herb yarrow and yarrow oil as a flavoring agent in foods. In addition, here are some uses that studies in humans have explored:

Wound Healing

Yarrow leaves, or juice made from its leaves, have historically been applied directly to wounds to aid healing. There isn’t much compelling research to support this use.

A randomized controlled trial of 140 women showed a positive effect of yarrow ointments on the healing of episiotomies (a small incision in the perineum that healthcare providers sometimes make during childbirth).

Yarrow has also been studied for its effects on cracked nipples due to breastfeeding. A study of 150 participants showed that yarrow helped, but not more than applying breastmilk or honey to the nipples.

Skin Inflammation

Yarrow is thought to act as an anti-inflammatory and antioxidant when applied to the skin. A randomized controlled trial in volunteers demonstrated that yarrow helped restore artificially irritated skin. Further study is needed.

Dysmenorrhea

There is sparse data supporting yarrow’s use in alleviating pain during menstrual cycles, although people use it anecdotally for this purpose. In one randomized controlled trial yarrow tea was shown to decrease the pain of people experiencing dysmenorrhea (painful menstrual cycles). Only 91 students were involved in the study and all were adolescents, so the effects could differ for other age groups.  

Multiple Sclerosis

A randomized controlled trial showed yearly relapses (acute attacks) decreased in people with multiple sclerosis who were given either 250 milligrams (mg) or 500 mg of yarrow daily for one year. In this study yarrow was given as add-on therapy, meaning it was offered in addition to maintenance medicines. People with multiple sclerosis who took yarrow along with their regular treatments showed improvements on cognitive tests. Further study is needed.

Irritable Bowel Syndrome

Yarrow is sometimes used in treating irritable bowel syndrome (IBS) because of its antispasmodic activity. This means it may decrease muscle spasms in the intestines and ease stomach cramping. So far, there is no substantial evidence to support this historical use.

A randomized controlled trial of 60 people with IBS showed that a mixture of yarrow and two other herbal supplements decreased symptoms. However, the result was not statistically significant. That means that the same thing could have happened simply by chance. Also, it is impossible to predict the effect of yarrow alone for IBS since it was given as a combination product in this trial.

Other Studied Conditions

While data in humans are lacking, some people also use yarrow for:

• Bacterial infections
• Respiratory viruses like COVID-19
• Regulating blood sugar in type 2 diabetes
• Anxiety
• Protecting the liver and gallbladder
• Cancer
• Chemotherapy-related toxicities
• Cosmetic uses

It’s important to highlight that most of these studies were done on mouse models or using cells in a lab. It is not known if the effects will be the same in humans. Further research in humans is needed before yarrow is given the green light for any of these uses.

What Are the Side Effects of Yarrow?

While yarrow is considered a "natural" product, keep in mind that even natural substances can have side effects and drug interactions. Think of these products as you would pharmaceutical drugs. Most of the available safety data come from studies in mice, so not enough is known about side effects in humans yet.

Common Side Effects

Yarrow is generally considered safe to use medicinally, but possible side effects may include:

• Skin irritation when used topically: Sesquiterpenes (a type of metabolite) in yarrow may cause contact dermatitis or skin rash.
• Increased urination: Yarrow had a diuretic effect in a rat model.

However, some groups of people may face additional risks from taking yarrow supplements.

Severe Side Effects

In one case report, a woman who consumed 5 cups a day of yarrow tea for one week went to the emergency room complaining of blurry vision, dry mouth, fatigue, and heart palpitations. These symptoms are consistent with anticholinergic toxicity (a harmful effect caused by halting the action of a neurotransmitter called acetylcholine), which can cause hallucinations, seizures, or coma in severe cases. 

Importantly, there is no data to confirm that yarrow has anticholinergic effects. However, if you experience these or any other symptoms after taking this supplement, go to the emergency room to be safe.

Precautions

Some groups of people may face additional risks from taking yarrow supplements:

Pregnancy and Breastfeeding

Yarrow is not recommended for use during pregnancy or breastfeeding. An ingredient of yarrow called thujone could increase the risk of miscarriage.

So far, not enough is known about the risk of yarrow during breastfeeding, so it's safest to avoid using it until after your baby is weaned. 

Infants and Children

Because of a lack of studies on safety or efficacy in children, use in this population is not recommended.

Allergies

If you're allergic to plants that are members of the Asteraceae/Compositae family, you may also be allergic to yarrow. Other plants in the family include:

• Chrysanthemums
• Daisies
• Marigolds
• Ragweed

If you have plant allergies but don't know for sure about this particular group of plants, talk to your healthcare provider before taking yarrow.

Increased Bleeding Risk

The research on this is quite limited, but yarrow contains the compound achilleine which reduces the time for blood clotting. Because yarrow could theoretically slow blood clotting, you should discuss its use with your healthcare provider before any surgeries. It may need to be stopped before the procedure.

Dosage: How Much Yarrow Should I Take?

There's no established standard dosing for yarrow, although daily dosing of up to 500 mg has been used safely for up to a year in one human study.

Always follow instructions on product labels and include your healthcare provider and pharmacist in your decisions. Look for yarrow supplementation certified by a third party if purchasing it in a store.

What Happens if I Take Too Much Yarrow?

There is insufficient data to predict the effects of taking too much yarrow. If you feel you've ingested too much yarrow, seek immediate guidance from a healthcare provider.

Interactions

There is very little evidence about yarrow's interactions with prescription medications or other herbal supplements. Yarrow may have a negative interaction with the following remedies, but these are primarily theoretical:

• Blood thinning medications: Anti-inflammatories, anticoagulants, and antiplatelet drugs slow blood clotting. Bleeding risk might be increased by taking yarrow.
• Medications to reduce stomach acid: Because yarrow may increase the production of stomach acid, it might interfere with over-the-counter and prescription drugs designed to decrease stomach acid.
• Sedatives: If taken with yarrow, they may cause excessive drowsiness.  
• Lithium: Yarrow may decrease your body's ability to get rid of lithium, increasing the risk of lithium build-up and severe side effects.

Thujone is a substance in yarrow, and at high doses, it is toxic to the brain and may cause seizures.

It is essential to read a supplement's ingredient list and nutrition facts panel carefully to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications. 

How to Store Yarrow

Most commercially available yarrow products can be safely stored at room temperature. Always follow package directions regarding storage and expiration dates. Keep this and all supplements and medications out of the reach of children and pets.

The plant leaves may be dried, though it is unknown how long to keep them on your shelf. Some suggest throwing yarrow out when its aroma begins to fade, as it may become less potent.

Similar Supplements

Many supplements are similarly touted for wound healing, including:

• Aloe 
• Chamomile
• Echinacea 
• Rosemary
• Saint John’s wort

Like yarrow, these herbs have been used extensively in traditional medicine and are available in several dosage forms. 

Sage, cedar leaf, and wormwood are other herbs that contain thujone. Like yarrow, these should not be used in pregnancy. Check with your healthcare provider before taking yarrow if you are also taking any of these supplements. At high doses, thujone may cause seizures, so the recommended maximum daily amount is 3 to 7 mg.

Sources of Yarrow and What to Look For

Sources of yarrow are the plant itself and supplements made from it.

Food Sources of Yarrow

The yarrow root may be ground up to make a spice. Flowers and leaves of the plant can be used as ingredients in soups or salads. Although yarrow is not a common ingredient in commercially available foods in the United States, it is approved by the FDA for use as a flavoring agent.

Yarrow Supplements

Yarrow is commercially available in various dosage forms, including herbal teas, capsules, essential oil, ointments, and tinctures. 

Essential oil or ointment applied to the skin may be preferable because of decreased systemic (body-wide) side effects.

Tinctures are highly concentrated extracts made by soaking the plant in alcohol. Doses are taken by mouth using a dropper. Because of the alcohol content (often 25% to 60%), this form may not be recommended in children or during pregnancy. Check with your child’s pediatrician or your OB/GYN before use.

Summary

Yarrow has a long history of use in folk medicine and has theoretical benefits for various health conditions. However, there is only weak evidence to support its use in humans. More robust human trials are needed before yarrow can be considered safe or effective. As with all supplements, discuss yarrow with your healthcare provider before adding it to your daily routine.