Drug & supplement interaction

Pyrethrum + Mechlorethamine Hydrochloride

Mechlorethamine Hydrochloride brand name: Valchlor.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Pyrethrum and Mechlorethamine Hydrochloride 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.

Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Pyrethrum and Mechlorethamine Hydrochloride

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 Mechlorethamine Hydrochloride and Pyrethrum 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Pyrethrum at all — not against Mechlorethamine Hydrochloride, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Pyrethrum safety at a glance

Pyrethrum overall Use caution Pyrethrum is an insecticide, not a dietary supplement, and should not be taken internally.
Pregnancy Avoid Avoid internal use and limit exposure to insecticide products during pregnancy due to lack of safety data.
Breastfeeding Avoid Avoid internal use while breastfeeding because safety has not been established.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Mechlorethamine Hydrochloride and Pyrethrum? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

What Pyrethrum Itself Has Been Linked To

This is not an interaction — nothing below involves Mechlorethamine Hydrochloride. It is the side-effect record for Pyrethrum on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Pyrethrum, this list is the first place to look. One entry is worth acting on rather than waiting out — marked below.

  • An allergic reaction Worth acting on Additional detail

    “Pyrethrum has limited toxicity. The symptoms of overdose include headache, tinnitus, nausea, tingling of fingers and toes, respiratory disturbances, and other symptoms of neurotoxicity (18). The pyrethrum flower or derivatives of it might cause an allergic reaction in individuals sensitive to the Asteraceae/Compositae family.”

    Pyrethrum · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 18. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  • Ringing in the ears / Numbness or tingling / Headache / Nausea Additional detail

    Recorded for Pyrethrum in the same Natural Medicines adverse-effect record shown under An allergic reaction above.

Everything above comes from the Natural Medicines adverse-effect record for Pyrethrum — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Mechlorethamine Hydrochloride’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Mechlorethamine Hydrochloride column appears here.

From our Q&A

Questions About Pyrethrum or Mechlorethamine Hydrochloride

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

This page covers Pyrethrum only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Mechlorethamine Hydrochloride page lists 10 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Acerola (moderate), Alpha-lipoic Acid (moderate), Coenzyme Q10 (moderate), Dimethylsulfoxide (dmso) (moderate) and Rose Hip (moderate).

By severity: 9 moderate · 1 minor.

From our pharmacist’s overview on the Mechlorethamine Hydrochloride page

“Mechlorethamine (Valchlor) is a chemotherapy gel applied to the skin for a form of lymphoma, and the 10 supplements on this page split into two groups. Seven are antioxidants, everyday products like vitamin C and turmeric, which in theory could blunt how well an alkylating chemotherapy drug works.”

Reviewed by 2 · Jul 18, 2026

Open the Mechlorethamine Hydrochloride interaction page

How much people look this up

Where Pyrethrum and Mechlorethamine Hydrochloride 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 Pyrethrum
Steady interest

#1,137 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Mechlorethamine Hydrochloride
Steady interest

#2,517 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 Pyrethrum reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Pyrethrum and Mechlorethamine Hydrochloride records this page draws on were last updated July 10, 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 Pyrethrum

What is Pyrethrum?

  • Natural insect repellent
  • Killing fleas, lice, and other pests
  • Garden and household insecticide
  • Traditional use against parasites

Pyrethrum is a daisy-like flower whose extracts (called pyrethrins) are widely used as a natural insecticide for plants, pets, and lice. It is not a supplement meant to be taken by mouth, and there is no good evidence supporting any internal health use. If you use pyrethrum products, treat them as pesticides and follow label directions carefully.

Tanacetum cinerariifolium · Asteraceae · Dried flower heads · Insecticide powders, sprays, and extracts (pyrethrins); rarely used internally

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

Pyrethrum: dosing

There is no established or recommended internal dose for pyrethrum, and it should not be taken as a supplement. For insecticide, lice, or flea products, the correct amount depends entirely on the specific product.Always follow the directions on the product label exactly, and do not use more or more often than directed.

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

Read the full Pyrethrum monograph & all interactions
Medication

About Mechlorethamine Topical

What Is Mechlorethamine Topical Used For?

Brand name: Valchlor

Valchlor (mechlorethamine gel applied to the skin) is approved to treat Stage IA and IB mycosis fungoides-type cutaneous T-cell lymphoma — a slow-growing cancer that primarily affects the skin. It is used in patients who have already received at least one prior skin-directed treatment.

Most-Reported Side Effects for Mechlorethamine Hydrochloride

From FAERS, the FDA’s public side-effect reporting system (2,244 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Pruritus 322 reports
Application site pruritus 224 reports
Application site erythema 220 reports
Application site pain 218 reports
Erythema 213 reports
See full Mechlorethamine Topical drug information
Keep checking

Other Drugs & Pyrethrum

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Pyrethrum list.

See the full Pyrethrum interactions page
See every supplement checked against Mechlorethamine Hydrochloride, ranked by severity
Evidence & sources

Pyrethrum References

The 3 references that drive our Pyrethrum 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. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  2. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
  3. Drugs in Pregnancy and Lactation. 4th ed. Baltimore, MD: Williams & Wilkins, 1994.

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 Pyrethrum and Mechlorethamine Hydrochloride Together: Common Questions

Is it safe to take Pyrethrum with Mechlorethamine Hydrochloride?
We do not list a known interaction between Pyrethrum and Mechlorethamine Hydrochloride. 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.
Does Mechlorethamine Hydrochloride interact with any supplements?
Yes. Mechlorethamine Hydrochloride has documented interactions with 10 supplements in our database — Pyrethrum is not one of them. The Mechlorethamine Hydrochloride 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

Pyrethrum monograph Uses, safety profile, and every drug interaction in one place Mechlorethamine Topical drug information The full plain-English guide to this medication Mechlorethamine Hydrochloride supplement interactions Every supplement checked against Mechlorethamine Hydrochloride, 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 3 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Mechlorethamine Hydrochloride and Pyrethrum?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.