Drug & supplement interaction

Henbane + Diphenhydramine

Diphenhydramine brand names: Benadryl, Dormin, Allerdryl, Valdrene, Sleep-Ettes D, and others.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Henbane has a major interaction with Diphenhydramine. Concomitant use of henbane can have additive anticholinergic effects and adverse effects with amantadine, antihistamines, atropine, belladonna alkaloids, hyoscyamine, phenothiazines, procainamide, scopolamine, and tricyclic antidepressants.

Read the full interaction report
SeverityMajor
LikelihoodProbable
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Henbane and Diphenhydramine

Here is the interaction we found between these two, with the evidence behind it.

Major

ANTICHOLINERGIC DRUGS

Why this applies to Diphenhydramine

Diphenhydramine falls under ANTICHOLINERGIC DRUGS — the group Henbane interacts with.

Concomitant use of henbane can have additive anticholinergic effects and adverse effects with amantadine, antihistamines, atropine, belladonna alkaloids, hyoscyamine, phenothiazines, procainamide, scopolamine, and tricyclic antidepressants.
Severity Major Likelihood Probable Evidence D

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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: both henbane and diphenhydramine (the active ingredient in Benadryl) have what we call anticholinergic effects. That means they both block acetylcholine, a messenger your body uses for things like saliva, sweat, focusing your eyes, emptying your bladder, and keeping your heart rate steady. Stack two of these together and the effects pile up.

So combining them could leave you with a very dry mouth, blurry vision, constipation, trouble urinating, a racing heart, confusion, or feeling overly drowsy or even agitated. This is a theoretical concern based on how these compounds work, but the direction is clear and the risk is real, especially in older adults. Honestly, I'd steer clear of henbane entirely since it can be genuinely toxic. Please talk with your pharmacist or doctor before mixing the two.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Henbane Also Interacts With Other Medications

Henbane has 194 major, known drug interactions in our database — the Diphenhydramine one above is one of them. If you take anything else, check it against the full list below.

Major 194 No known interaction 2,636 (incl. Diphenhydramine)
Taking anything else?

Check Another of Your Medications Against Henbane

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

From our Q&A

Questions About Henbane or Diphenhydramine

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

This page covers Henbane only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Diphenhydramine page lists 147 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 119 moderate · 19 minor.

From our pharmacist’s overview on the Diphenhydramine page

“Diphenhydramine (Benadryl, Simply Sleep) is sedating by design, and most of the 147 supplements and herbal ingredients on this list lean into that. Seventy-eight are sedating substances themselves, alcohol and kava the standouts, and stacking them can slow breathing and reflexes well beyond ordinary drowsiness.”

Reviewed by 2 · Jul 18, 2026

Open the Diphenhydramine interaction page

One more smart check

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

We hold 6 real supplement products containing Henbane, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Henbane. Your product may carry other ingredients that interact with Diphenhydramine too, on top of Henbane — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Henbane and Diphenhydramine 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 Henbane
Steady interest

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

29 days ago today
Medication Diphenhydramine
Top half

#738 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.

Supplement

About Henbane

What is Henbane?

Henbane
  • Pain relief
  • Muscle spasms and cramps
  • Sleep and sedation
  • Asthma and breathing problems (traditional)
  • Toothache (traditional)

Henbane is a highly poisonous plant containing potent alkaloids like hyoscyamine and scopolamine, and even small amounts can cause serious or deadly poisoning. While its compounds have real medical uses, these belong in carefully controlled prescription drugs, not in self-made or self-dosed herbal products. We strongly advise against using henbane as a supplement.

Read the full Henbane monograph & all interactions
Medication

About Diphenhydramine

What Is Diphenhydramine Used For?

Brand names: Benadryl, Dormin, Allerdryl, Valdrene, Sleep-Ettes D, Simply Sleep, Sominex, Diphenhydramine, Compoz, Sleep Aid, Benadryl cream, Benadryl spray, Dermamycin cream, Ziradryl, Nytol

Diphenhydramine temporarily relieves symptoms of hay fever, other upper respiratory allergies, and the common cold — including runny nose, sneezing, itchy or watery eyes, and itching of the nose or throat.

After Bite Xtra gel is formulated for topical use and is approved to temporarily relieve pain and itching from minor burns, minor cuts and scrapes, insect bites, minor skin irritations, and rashes from poison ivy, poison oak, and poison sumac.

See full Diphenhydramine drug information
Keep checking

Other Drugs & Henbane

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

194Major
0Moderate
0Minor
2,635No known interaction
194 Major 2,635 No interaction
Major

194 interactions

Showing 60 of 194 major interactions — see all 194 on the Henbane page.

No interaction 2,635 drugs checked — show the list

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

Showing the 60 most looked-up of 2,635 medications checked with no known interaction — see the full Henbane list.

See the full Henbane interactions page
See every supplement checked against Diphenhydramine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

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.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Henbane monograph › Uses, safety, and every drug interaction in one place Diphenhydramine supplement interactions › Every supplement checked against Diphenhydramine, ranked by severity Diphenhydramine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Henbane and Diphenhydramine Together: Common Questions

Can you take Henbane with Diphenhydramine?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Henbane and Diphenhydramine interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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

Still Have a Question About Diphenhydramine and Henbane?

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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.