Herb & supplement monograph

Marsh Labrador Tea Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Marsh Labrador Tea interacts with medications. The heart of this page is the interaction list — every drug Marsh Labrador Tea is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Marsh Labrador Tea is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Marsh Labrador Tea Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Marsh Labrador Tea drug interaction appears low for most people, though anyone taking sedating medicines should use extra care. None of the listed interactions are rated major, and the single concern behind the entire list rests on limited research rather than well-documented human studies.

Interactions deserving the most attention

The one interaction worth real attention involves CNS depressants, the broad group of medicines that slow brain activity. Research suggests Marsh Labrador tea may potentiate the effects of barbiturates and alcohol, which could mean more drowsiness or slowed thinking when they are combined. This has not been confirmed in well-controlled human studies, but because deeper sedation can matter for safety, we treat it as a reasonable precaution rather than a proven harm.

What the rest of the list means

Although hundreds of medications appear on the interaction list, they all trace back to this one sedation concern applied across an entire drug class. A long list like this does not mean each combination is known to be harmful; it reflects a predicted effect that has not been clearly demonstrated in people. For most other medicines, no interaction has been reported at all.

Check your medications against Marsh Labrador Tea

Based on HelloPharmacist’s Marsh Labrador Tea interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Marsh Labrador Tea

248 medications have a known interaction with Marsh Labrador Tea, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Marsh Labrador Tea using our pharmacist-reviewed interaction data.

AI summaries are generated from our Marsh Labrador Tea interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Marsh Labrador Tea combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Marsh Labrador Tea affects

Every type of medication (drug category) Marsh Labrador Tea is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 1 drug category Marsh Labrador Tea interacts with

Cns Depressants

Marsh Labrador tea can potentiate effects of barbiturates and alcohol.

Likelihood Possible Evidence D

Monograph

Marsh Labrador Tea: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Marsh Labrador tea is a bog-growing shrub used in folk medicine for coughs, colds, and skin problems, but high-quality human evidence for any use is lacking. Because it contains grayanotoxins (andromedotoxin) that can be poisonous, it is not considered safe for routine use, and pregnant or breastfeeding people should avoid it.

Scientific name: Rhododendron tomentosum
Family: Ericaceae
Part used: Leaves and flowering twigs (and an essential oil distilled from them)
Common forms: Tea (infusion), essential oil, topical preparations

People commonly use it for

Colds and respiratory complaints
Cough and congestion
Mild aches and joint discomfort
Topical relief of skin irritation, swelling, and insect bites
Traditional use as a diuretic

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

The plant contains toxic grayanotoxins, so any internal use carries a risk of poisoning.

PregnancyLikely Unsafe

When used orally; avoid using. Marsh Labrador tea is considered to be a potential uterine stimulant and abortifacient.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Marsh Labrador tea (Rhododendron tomentosum, formerly called Ledum palustre) is a low, evergreen shrub in the heath family (Ericaceae). It produces small white or pink flowers and has narrow leaves with a strong, resinous smell. As its name suggests, it grows in wet, acidic places such as bogs, swamps, and damp northern forests across North America, Europe, and Asia.

For centuries, people in northern cultures have brewed the leaves and twigs into a tea or used the plant in topical remedies. It is important not to confuse it with true Labrador tea (Rhododendron groenlandicum), although the two are related and sometimes used in similar ways.

Despite its long folk history, Marsh Labrador tea is not a well-studied supplement, and it contains naturally occurring toxins, so it should be approached carefully.

How it works

The leaves contain an aromatic essential oil rich in compounds such as ledol and other terpenes, along with flavonoids and tannins. The tannins may explain its astringent (tightening) effect, and the volatile oils give it its strong scent and possible mild antimicrobial activity in laboratory tests.

The plant also contains grayanotoxins (sometimes called andromedotoxin), which are the same family of toxic compounds found in other rhododendrons. These affect nerve and muscle cell channels and are responsible for the plant's poisonous potential.

It is important to understand that most of these proposed actions come from test-tube or animal studies. They do not prove the herb is safe or effective in people.

Effectiveness

Does Marsh Labrador Tea work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 4 uses evaluated

4 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Marsh Labrador Tea, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 4 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Back pain

Rating & evidence shown verbatim from Natural Medicines

Topical marsh Labrador tea has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Insect bite

Rating & evidence shown verbatim from Natural Medicines

Topical marsh Labrador tea has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Osteoarthritis

Rating & evidence shown verbatim from Natural Medicines

Topical marsh Labrador tea has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Postoperative swelling

Rating & evidence shown verbatim from Natural Medicines

Topical marsh Labrador tea has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

The biggest safety concern is the plant's grayanotoxin content. Eating large amounts, drinking strong or long-steeped tea, or using concentrated essential oil can cause poisoning. Symptoms may include nausea, vomiting, diarrhea, dizziness, low blood pressure, slow heartbeat, and trouble breathing.

Because the toxin level can vary from plant to plant, there is no reliably "safe" amount, and self-prepared teas are especially risky. The essential oil should never be taken by mouth.

Pregnancy: Avoid. The plant has a traditional reputation for causing miscarriage and contains toxic compounds, so it should not be used during pregnancy. Breastfeeding: Avoid, because there is not enough safety information and the toxins could pass to the baby. Children, older adults, and people with heart, kidney, or liver problems should also avoid it. Always talk to a pharmacist or doctor before using any product containing this plant.

Side effects

Even in modest amounts, the tea may cause stomach upset, nausea, or drowsiness. Larger amounts can lead to vomiting, diarrhea, headache, dizziness, sweating, and a feeling of being unwell.

In more serious poisoning, grayanotoxins can cause low blood pressure, a dangerously slow or irregular heartbeat, weakness, and difficulty breathing. These effects can be medical emergencies. Applied to the skin, the plant or its oil may cause irritation in some people.

If you suspect poisoning after consuming this plant, seek medical care or contact a poison control center right away.

Marsh Labrador Tea: Reported Adverse Effects

Documented safety reports on Marsh Labrador Tea from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Orally, large amounts of marsh Labrador tea can cause poisoning due to its ledol constituent. The essential oil of marsh Labrador tea can cause severe irritation of the gastrointestinal tract, vomiting, diarrhea, irritation and damage to the kidneys and urinary tract, heavy perspiration, myalgias, and arthralgias. It can also cause central nervous system excitation with narcotic intoxication, seizures, paralysis, and even death. The content of ledol in marsh Labrador tea is unpredictable, and seems to range from 3.9% to 30.5% depending on the geographical source.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
Dampc A, Luczkiewicz M. Bog Labrador tea--the aromatic beverage and spice: a review of origin, processing and safety. J Sci Food Agric. 2015;95(8):1577-83.

Reports by condition

Diarrhea Gastrointestinal

Orally, ledol, a constituent of the essential oil of marsh Labrador tea, can cause gastrointestinal irritation resulting in vomiting, gastroenteritis, and diarrhea.

Dampc A, Luczkiewicz M. Bog Labrador tea--the aromatic beverage and spice: a review of origin, processing and safety. J Sci Food Agric. 2015;95(8):1577-83.

Epilepsy Neurologic/CNS

Orally, ledol, a constituent of marsh Labrador tea essential oil, can cause central nervous system excitation in a dose-dependent manner. Small amounts of ledol can lead to mild stimulating effects similar to caffeine, while larger doses can lead to spasms, seizures, paralysis, and even death.

Dampc A, Luczkiewicz M. Bog Labrador tea--the aromatic beverage and spice: a review of origin, processing and safety. J Sci Food Agric. 2015;95(8):1577-83.

Knee pain Musculoskeletal

Orally, the essential oil of marsh Labrador tea can cause myalgias and arthralgias.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no established safe or standardized dose for Marsh Labrador tea. Because the plant naturally contains toxic grayanotoxins, even traditional preparations carry risk, and stronger or longer brews increase that risk.

If you choose to use a commercial product, follow the directions on the label exactly and do not exceed them. Never assume that "natural" means harmless. Homeopathic "Ledum" products are highly diluted and are dosed differently than herbal teas.

The safest approach is to speak with a pharmacist or doctor before using any form of this plant, and to avoid making concentrated home preparations.

Pregnancy & Breastfeeding

Marsh Labrador Tea & Pregnancy

Likely Unsafe

When used orally; avoid using. Marsh Labrador tea is considered to be a potential uterine stimulant and abortifacient.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

Marsh Labrador Tea & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 3 references that drive our Marsh Labrador Tea monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
Dampc A, Luczkiewicz M. Bog Labrador tea--the aromatic beverage and spice: a review of origin, processing and safety. J Sci Food Agric. 2015;95(8):1577-83. PubMed

Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

Pharmacist Counseling Corner

Marsh Labrador Tea: Common Questions

What is Marsh Labrador Tea used for, and does it work?

People use Marsh Labrador Tea for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.

Does Marsh Labrador Tea interact with prescription medications?

Yes. We list 248 medications with a known interaction with Marsh Labrador Tea. Use the checker above to see how Marsh Labrador Tea interacts with a specific drug.

How are Marsh Labrador Tea interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Marsh Labrador Tea with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Marsh Labrador Tea interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

What is Marsh Labrador Tea used for?

It has been used in traditional medicine mostly for colds, coughs, and respiratory complaints, as a diuretic, and on the skin for swelling, bites, and minor wounds. There is little solid scientific evidence that it works for any of these.

Is Marsh Labrador Tea safe to drink?

It is not considered reliably safe because it contains grayanotoxins (andromedotoxin), which can cause poisoning. Strong or large amounts can lead to vomiting, dizziness, a slow heartbeat, and breathing problems.

Can I use it while pregnant or breastfeeding?

No. It should be avoided during pregnancy because of a traditional link to miscarriage and its toxic compounds, and it should be avoided while breastfeeding due to a lack of safety data.

Is Marsh Labrador Tea the same as Labrador tea?

Not exactly. Marsh Labrador Tea is Rhododendron tomentosum, while "true" Labrador tea is the related Rhododendron groenlandicum. They are sometimes confused, but they are different plants with different traditional uses.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Marsh Labrador Tea Drug Interactions, Uses, Effectiveness, Safety & More

Your Choice:

Marsh Labrador Tea Drug Interactions: The Bottom Line

Drugs that interact with Marsh Labrador Tea

Don’t want to scroll the list? Just ask.

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Likelihood — How Well It’s Documented

Where This Data Comes From

The kinds of drugs Marsh Labrador Tea affects

Marsh Labrador Tea: Uses, Safety & Side Effects

Overview

How it works

Does Marsh Labrador Tea work?

Safety & precautions

Side effects

Marsh Labrador Tea: Reported Adverse Effects

Dosing

Marsh Labrador Tea & Pregnancy

Marsh Labrador Tea & Breastfeeding

References & further reading

Marsh Labrador Tea: Common Questions

Related supplements & herbs

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