Drug & supplement interaction

Horseradish + Ketoconazole

Ketoconazole brand name: Nizoral.

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 Horseradish and Ketoconazole 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

Horseradish and Ketoconazole

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 Ketoconazole and Horseradish 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.

Horseradish safety at a glance

Horseradish overall Use caution Food amounts are generally safe, but concentrated supplements may irritate the digestive tract and mucous membranes.
Pregnancy Avoid Avoid medicinal amounts during pregnancy because safety has not been established.
Breastfeeding Likely Safe When the root is used orally in amounts commonly found in foods. Horseradish has Generally Recognized as Safe (GRAS) status in the US. Read the full breastfeeding detail

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 Ketoconazole and Horseradish? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Ketoconazole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Ketoconazole is filed under 8 classifications — including antifungals, cytochrome p450 2c19 (cyp2c19) inhibitors, cytochrome p450 2c9 (cyp2c9) inhibitors. Horseradish has documented interactions with 1 drug class — the most serious being thyroid hormone (moderate) — and none of Ketoconazole’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

Horseradish Does Interact With Other Medications

Horseradish has 16 moderate known drug interactions in our database — Ketoconazole isn’t one of them. If you take anything else, check it against the full list below.

Moderate 16 No known interaction 2,814 (incl. Ketoconazole)
Taking anything else?

Check Another of Your Medications Against Horseradish

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

What to actually watch for

No Interaction Found — But Data Suggests Horseradish and Ketoconazole 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.

  • Stomach upset / Diarrhea / Vomiting Additional detail

    Horseradish

    “Orally, consuming large amounts of horseradish can cause gastrointestinal upset, bloody vomiting and diarrhea (2,6), and irritation of mucous membranes (2,4).”

    Horseradish · Natural Medicines adverse-effect record, reported in diarrhea.

    3 sources cited
    1. 2. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
    2. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
    3. 4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

    Ketoconazole

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

Reported for Horseradish but not commonly for Ketoconazole: an allergic reaction, sweating, a fast or pounding heartbeat and fainting.

Effects for Ketoconazole come from the ADVERSE REACTIONS section of its FDA label; effects for Horseradish come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Horseradish in Pregnancy & Breastfeeding

Lactation Likely Safe

When the root is used orally in amounts commonly found in foods. Horseradish has Generally Recognized as Safe (GRAS) status in the US.

Lactation Likely Unsafe

When used orally in large amounts. The mustard oils produced by glucosinolates from horseradish are considered toxins that can be excreted through breast milk.

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

From our Q&A

Questions About Horseradish or Ketoconazole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Horseradish or Ketoconazole, 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 Ketoconazole

This page covers Horseradish only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ketoconazole page lists 182 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 135 moderate · 41 minor.

From our pharmacist’s overview on the Ketoconazole page

“Ketoconazole (Nizoral) is already hard on the liver, so treat its 182 interacting supplements with genuine care, starting with the six rated major. Most of the list runs through CYP3A4, the liver enzyme ketoconazole strongly blocks, so it can raise levels of over a hundred herbal ingredients, while grapefruit pushes ketoconazole itself…”

Reviewed by 2 · Jul 18, 2026

Open the Ketoconazole interaction page

One more smart check

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

We hold 245 real supplement products containing Horseradish, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Horseradish. Even though Horseradish itself has no known interaction with Ketoconazole, 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 Horseradish and Ketoconazole 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 Horseradish
Top half

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

29 days ago today
Medication Ketoconazole
Steady interest

#1,816 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 Horseradish reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Horseradish and Ketoconazole 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 Horseradish

What is Horseradish?

  • Sinus and respiratory congestion
  • Urinary tract infections
  • Digestive support
  • Antimicrobial
  • Culinary flavoring

Horseradish is a pungent root used as a food and folk remedy, most often for sinus congestion and urinary tract complaints. Human evidence is limited, and while culinary amounts are generally well tolerated, concentrated supplements can irritate the stomach and should be used cautiously. Talk with your pharmacist or doctor before using horseradish as a medicine.

Armoracia rusticana · Brassicaceae · Root (fresh or dried) · Fresh grated root, dried root powder, prepared condiment (sauce), capsules, tinctures

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

Horseradish: dosing

There is no well-established standardized medicinal dose for horseradish. Amounts used in research and traditional practice vary widely depending on the form (fresh root, dried powder, or extract).If you use a commercial supplement, follow the directions on the product label and do not exceed the recommended amount. Avoid taking large or concentrated amounts in hopes of stronger effects, since this mainly increases the risk of irritation and side effects.

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

Read the full Horseradish monograph & all interactions
Medication

About Ketoconazole

What Is Ketoconazole Used For?

Brand name: Nizoral

Ketoconazole 2% shampoo and foam are used to treat tinea versicolor (also called pityriasis versicolor) — a fungal infection caused by Pityrosporum orbiculare (also known as Malassezia furfur), a yeast that naturally lives on the skin.

This infection creates light or dark patches, most often on the trunk, neck, arms, and upper thighs. Even after the fungus is cleared, those skin patches may take months to return to their normal color — that's normal, and depends on your skin type and sun exposure. Tinea versicolor can also come back, since the fungus lives on healthy skin even when there's no active infection.

Most-Reported Side Effects for Ketoconazole

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Pruritus 984 reports
Fatigue 975 reports
Nausea 873 reports
Rash 858 reports
Diarrhea 814 reports
See full Ketoconazole drug information
Keep checking

Other Drugs & Horseradish

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

0Major
16Moderate
0Minor
2,813No known interaction
16 Moderate 2,813 No interaction
Moderate

16 interactions

No interaction 2,813 drugs checked — show the list

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

Showing the 60 most looked-up of 2,813 medications checked with no known interaction — see the full Horseradish list.

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

Horseradish References

The 6 references that drive our Horseradish 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. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
  2. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  3. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  4. Electronic Code of Federal Regulations. Title 21. Part 182 -- Substances Generally Recognized As Safe. Available at: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=182
  5. Panter, K. E. and James, L. F. Natural plant toxicants in milk: a review. J Anim Sci 1990;68(3):892-904. PubMed
  6. Lehmann CU, Puckett AL, Betz BO. 56-year-old man - increased heart rate - weakness - intense sweating - horseradish consumption - Dx?. J Fam Pract 2022;71(7):317-321. PubMed

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 Horseradish and Ketoconazole Together: Common Questions

Is it safe to take Horseradish with Ketoconazole?
We do not list a known interaction between Horseradish and Ketoconazole. 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 Horseradish and Ketoconazole 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.
How was the Horseradish and Ketoconazole combination checked?
Interactions in our licensed database are recorded against drug classes. Ketoconazole is filed under 8 classifications, and Horseradish has documented interactions with 1 drug class — none of Ketoconazole'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 Horseradish interact with any other medications?
Yes. Horseradish has 16 documented drug interactions in our database — Ketoconazole 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 Ketoconazole interact with any supplements?
Yes. Ketoconazole has documented interactions with 182 supplements in our database — Horseradish is not one of them. The Ketoconazole 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

Horseradish monograph Uses, safety profile, and every drug interaction in one place Ketoconazole drug information The full plain-English guide to this medication Ketoconazole supplement interactions Every supplement checked against Ketoconazole, 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 6 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Ketoconazole and Horseradish?

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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.