Drug & supplement interaction

Calendula + Metronidazole

Metronidazole brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, and others.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Calendula and Metronidazole in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Calendula and Metronidazole

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Metronidazole and Calendula in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Calendula safety at a glance

Calendula overall Use caution Generally well tolerated on the skin, but can cause allergic reactions in sensitive people.
Pregnancy Likely Unsafe When used orally; contraindicated due to spermatocide, antiblastocyst, and abortifacient effects. There is insufficient reliable information available about the... Read the full pregnancy detail
Breastfeeding Use caution Reliable safety information is lacking, so it is best to avoid oral use unless your doctor approves.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Metronidazole and Calendula? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Metronidazole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Metronidazole is filed under 8 classifications — including cytochrome p450 2c9 (cyp2c9) inhibitors, qt interval-prolonging drugs, cytochrome p450 3a4 (cyp3a4) inhibitors. Calendula has documented interactions with 1 drug class — the most serious being cns depressants (minor) — and none of Metronidazole’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Calendula Does Interact With Other Medications

Calendula has 248 minor known drug interactions in our database — Metronidazole isn’t one of them. If you take anything else, check it against the full list below.

Minor 248 No known interaction 2,582 (incl. Metronidazole)
Taking anything else?

Check Another of Your Medications Against Calendula

Covers the 2,830 medications we’ve checked against Calendula. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Calendula and Metronidazole May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. 2 of them are worth acting on rather than waiting out — marked below.

  • Hives / An allergic reaction Worth acting on reported in 4.9% of FDA reports for Metronidazole Additional detail

    Calendula

    “Orally, calendula can cause allergic reactions. Topically, calendula can cause eczematous allergic reactions. Calendula-specific patch testing is recommended prior to usage to determine allergenic potential. Testing is particularly necessary in individuals sensitive to the Asteraceae/Compositae family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many other herbs.”

    Calendula · Natural Medicines adverse-effect record, reported in allergic rhinitis (hay fever).

    4 sources cited
    1. 10691. Reider N, Komericki P, Hausen BM, et al. The seamy side of natural medicines: contact sensitization to arnica (Arnica montana L.) and marigold (Calendula officinalis L.). Contact Dermatitis 2001;45:269-72..
    2. 11458. Paulsen E. Contact sensitization from Compositae-containing herbal remedies and cosmetics. Contact Dermatitis 2002;47:189-98. PubMed
    3. 96647. Madisetti M, Kelechi TJ, Mueller M, Amella EJ, Prentice MA. Feasibility, acceptability, and tolerability of RGN107 in the palliative wound care management of chronic wound symptoms. J Wound Care. 2017;26(Sup1):S25-S34. PubMed
    4. 11152. Gol'dman II. [Anaphylactic shock after gargling with an infusion of Calendula]. Klin Med (Mosk) 1974;52:142-3.

    Metronidazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Metronidazole, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • Itching Additional detail

    Calendula

    “Topically, a preparation containing calendula powder 0.1% resulted in inflammation around the wound to which it was applied. Burning sensation, itching, redness, and scaling were reported rarely in patients applying a combination of calendula, licorice, and snail secretion filtrate to the face. The specific role of calendula is unclear.”

    Calendula · Natural Medicines adverse-effect record, reported in pruritus.

    2 sources cited
    1. 96647. Madisetti M, Kelechi TJ, Mueller M, Amella EJ, Prentice MA. Feasibility, acceptability, and tolerability of RGN107 in the palliative wound care management of chronic wound symptoms. J Wound Care. 2017;26(Sup1):S25-S34. PubMed
    2. 110322. Puaratanaarunkon T, Washrawirul C, Chuenboonngarm N, Noppakun N, Asawanonda P, Kumtornrut C. Efficacy and safety of a facial serum containing snail secretion filtrate, Calendula officinalis, and Glycyrrhiza glaba root extract in the treatment of maskne: A

    Metronidazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Metronidazole. Read the label on DailyMed ›

Reported for Calendula but not commonly for Metronidazole: a severe allergic reaction.

Effects for Metronidazole come from the ADVERSE REACTIONS section of its FDA label; effects for Calendula come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 64,630 voluntary FDA FAERS reports for Metronidazole that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Calendula in Pregnancy & Breastfeeding

Pregnancy Likely Unsafe

When used orally; contraindicated due to spermatocide, antiblastocyst, and abortifacient effects. There is insufficient reliable information available about the safety of calendula when used topically during pregnancy.

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.© 2026 Therapeutic Research Center

Overlapping uses

What Metronidazole Is Prescribed For, and What Calendula Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Metronidazole is a prescription medicine with approved uses on its FDA label. Calendula is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Metronidazole is prescribed for: Metronidazole treats three main types of infections. It's used for trichomoniasis (a sexually transmitted parasitic infection), amebiasis (an intestinal or liver infection caused by a parasite), and serious anaerobic bacterial infections — infections caused by bacteria that thrive without oxygen, which can affect the abdomen, skin, bones, lungs, and other areas. Because sexual partners can pass trichomoniasis back and forth, both partners are typically treated at the same time, even if one has no symptoms.

Calendula has been studied for:

  • Bacterial vaginosis studied, not established Calendula has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Calendula for bacterial vaginosis

    It is unclear if topical calendula is beneficial for improving bacterial vaginosis.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Metronidazole on your own; if you are taking Calendula for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Calendula or Metronidazole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Calendula or Metronidazole, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Metronidazole

This page covers Calendula only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metronidazole page lists 83 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Cesium (major) and Ephedra (major).

By severity: 7 major · 63 moderate · 13 minor.

From our pharmacist’s overview on the Metronidazole page

“Metronidazole (Flagyl) can stretch the heart's QT interval on its own, and most of the seven major-rated interactions among its 83 flagged supplement ingredients do the same thing, so I read this list with more wariness than most antibiotics earn. Grapefruit and ephedra stand out for adding to that heart-rhythm risk, while activated ch…”

Reviewed by 2 · Jul 18, 2026

Open the Metronidazole interaction page

One more smart check

Taking Calendula as Part of a Dietary Supplement Product? Check It for Interactions

We hold 214 real supplement products containing Calendula, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Calendula. Even though Calendula itself has no known interaction with Metronidazole, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Calendula and Metronidazole Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Calendula
Top half

#537 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Metronidazole
Top 25%

#565 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Calendula reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Calendula and Metronidazole records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Calendula

What is Calendula?

Calendula
  • Minor wounds and skin healing
  • Skin inflammation and irritation
  • Diaper rash
  • Mouth and throat inflammation
  • Soothing dry or chapped skin

Calendula is a flowering plant whose petals are used mainly in skin creams, oils, and ointments to soothe minor irritation and support wound healing. Some early research is promising for skin and mouth uses, but the overall evidence is limited. It is generally well tolerated on the skin, but people allergic to ragweed, daisies, or marigolds should be cautious.

Calendula officinalis · Asteraceae · Flowers (petals/florets) · Topical creams, ointments, gels, oils, tinctures, teas, mouth rinses

An interaction check asks whether these two react with each other — it does not ask whether Calendula is a good idea for someone in your situation. Here is what our Calendula record says about it on its own.

Calendula: dosing

There is no official, standardized dose for calendula. The amount used depends on the product and how it is being used, such as a cream, oil, tincture, or tea.The best approach is to follow the directions on the product label and to choose products from reputable brands.

From our Calendula monograph — the full record covers uses, side effects and every documented interaction.

Read the full Calendula monograph & all interactions
Medication

About Metronidazole

What Is Metronidazole Used For?

Brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, MetroGel, Flagyl IV, Metronidazole Redi-Infusion, Flagyl IV RTU, Metro IV, Anabact, Metrosa, Metrotop, Noritate, Rozex Cream, Rozex Gel, Zyomet, Likmez

Metronidazole treats three main types of infections. It's used for trichomoniasis (a sexually transmitted parasitic infection), amebiasis (an intestinal or liver infection caused by a parasite), and serious anaerobic bacterial infections — infections caused by bacteria that thrive without oxygen, which can affect the abdomen, skin, bones, lungs, and other areas.

Because sexual partners can pass trichomoniasis back and forth, both partners are typically treated at the same time, even if one has no symptoms.

Most-Reported Side Effects for Metronidazole

From FAERS, the FDA’s public side-effect reporting system (64,630 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Nausea 4,812 reports
Diarrhea 4,197 reports
Vomiting 3,393 reports
Fever 3,294 reports
Drug hypersensitivity 3,160 reports
See full Metronidazole drug information
Keep checking

Other Drugs & Calendula

Browse every other medication we’ve checked against Calendula — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
248Minor
2,581No known interaction
248 Minor 2,581 No interaction
Minor

248 interactions

Showing 60 of 248 minor interactions — see all 248 on the Calendula page.

No interaction 2,581 drugs checked — show the list

We also checked Calendula against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,581 medications checked with no known interaction — see the full Calendula list.

See the full Calendula interactions page
See every supplement checked against Metronidazole, ranked by severity
Evidence & sources

Calendula References

The 9 references that drive our Calendula 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.

  1. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. Reider N, Komericki P, Hausen BM, et al. The seamy side of natural medicines: contact sensitization to arnica (Arnica montana L.) and marigold (Calendula officinalis L.). Contact Dermatitis 2001;45:269-72..
  3. Gol'dman II. [Anaphylactic shock after gargling with an infusion of Calendula]. Klin Med (Mosk) 1974;52:142-3.
  4. Paulsen E. Contact sensitization from Compositae-containing herbal remedies and cosmetics. Contact Dermatitis 2002;47:189-98. PubMed
  5. Bojadjiev C. On the sedative and hypotensive effect of preparations from the plant Calendula officinalis. Nauch Trud Visshi Med Inst Sof 1964;43:15-20.
  6. Samochowiec L. Pharmacological study of saponosides from Aralia mandshurica Rupr. et Maxim and Calendula officinalis L. Herba Pol. 1983;29:151-155.
  7. Madisetti M, Kelechi TJ, Mueller M, Amella EJ, Prentice MA. Feasibility, acceptability, and tolerability of RGN107 in the palliative wound care management of chronic wound symptoms. J Wound Care. 2017;26(Sup1):S25-S34. PubMed
  8. Final Assessment report on Calendula officinalis L., flos. European Medicines Agency: Committee on Herbal Medicinal Products (HMPC). 2018. EMA/HMPC/603409/2017. Available at: https://www.ema.europa.eu/en/documents/herbal-report/final-assessment-report-cal
  9. Puaratanaarunkon T, Washrawirul C, Chuenboonngarm N, Noppakun N, Asawanonda P, Kumtornrut C. Efficacy and safety of a facial serum containing snail secretion filtrate, Calendula officinalis, and Glycyrrhiza glaba root extract in the treatment of maskne: A

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Calendula and Metronidazole Together: Common Questions

Is it safe to take Calendula with Metronidazole?
We do not list a known interaction between Calendula and Metronidazole. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Calendula and Metronidazole have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Calendula and Metronidazole used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Calendula in each. That is a conversation for your prescriber, especially if Metronidazole is being adjusted to a target.
How was the Calendula and Metronidazole combination checked?
Interactions in our licensed database are recorded against drug classes. Metronidazole is filed under 8 classifications, and Calendula has documented interactions with 1 drug class — none of Metronidazole's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Calendula interact with any other medications?
Yes. Calendula has 248 documented drug interactions in our database — Metronidazole is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Metronidazole interact with any supplements?
Yes. Metronidazole has documented interactions with 83 supplements in our database — Calendula is not one of them. The Metronidazole interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Calendula monograph Uses, safety profile, and every drug interaction in one place Metronidazole drug information The full plain-English guide to this medication Metronidazole supplement interactions Every supplement checked against Metronidazole, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 9 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Metronidazole and Calendula?

Our pharmacists answer your medication & supplement questions — free.

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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.